Module 3 i

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Module 3 Questions

1) In a DC motor the stator magnetic field due to armature reaction moves

a) In the sane direction of rotation

b) In the opposite direction to rotation

c) In alignment with GNA

2) A 20 Pico farad capacitor with a 1MW resistor takes how long to charge

a) 20m seconds

b) 1 second

c) 10 seconds

3) Heat exposed to a material will

a) Make all materials harder to magnetise

b) Make all materials easier to magnetise

c) Have no effect on magnetism

4) A transformer has 2000v, 500 turns on the primary and 50 turns on the secondary. What would be the line voltage if the transformer were Delta/Star connected?

a) 200v

b) 346v

c) 450v

5) A transformer to supply a 24v load with a 5:1 turns ratio will have what primary supply?

a) 120v DC

b) 48v AC

c) 120v AC

6) A transformer has 750 primary turns and 4500 secondary, its turns ratio is

a) 6:1

b) 1:6

c) 1/6

7) A band stop filter will

a) Pass all frequencies either side of the band

b) Stop all frequencies either side of the band

c) Stop all frequencies

8) What is this circuit?

a) High Pass Filter

b) Low Pass Filter

c) Band Stop

9) In this circuit, Rx is equal to

a) R3 x R2 ¸ R4

b) R3 x R4 ¸ R2

c) R2 x R3 ¸ R4

10) A parallel circuit with any number of 2 terminal connections

a) Has the same current throughout

b) The sum of the individual voltage drops is equal to the emf

c) The resistance is dependent on current

11) 2 coils, which are turned from being in parallel to 90° but in close proximity, will have its mutual inductance

a) Decreased

b) Remain the same

c) Increase

12) If armature speed is doubled and field strength halved, field strength will

a) Halve

b) Remain the same

c) Double

13) In a circuit with voltage and current which is purely resistive will have its voltage with respect to current

a) In phase

b) 90° Leading

c) 90° Lagging

14) Average value of voltage is equal to

a) 1.1

b) 0.627 x Peak

c) 0.707 x Peak

15) What wave shape is used to control sweep in a CRT?

a) Sine wave

b) Square wave

c) Saw tooth

16) In a 3 phase AC motor, if one phase goes open circuit the motor with a light constant load will

a) Stop

b) Run slowly

c) Run normally

17) Line voltage in a Wye wound transformer is

a) Ö3 ¸ Phase voltage

b) Same as phase voltage

c) Ö3 x Phase voltage

18) To calculate generator output you need to know

a) Armature speed and number of series conductors

b) Field strength and number of armature parallel conductors

c) Series field strength and armature speed

19) What charge does an electron have?

a) Positive

b) No charge

c) Negative

20) An atom, which has gained an electron, will become

a) A negative ion

b) A positive ion

c) A neutral atom

21) An atom, which has few electrons in its valency (less than 4), will have

a) Low resistance

b) High resistance

c) No resistance

22) A 40AH battery will supply 200mA for

a) 250 hrs

b) 40 hrs

c) 200 hrs

23) A 24v, 10 A circuit wit 0.5W resistance will have what power

a) 50W

b) 100W

c) 150W

24) An electrolytic capacitor is used where

a) There is a polarised supply

b) Light loads are used

c) Low frequencies are used

25) A combined starter generator has a

a) Low resistance shunt field and high resistance series field

b) Low resistance series field and high resistance shunt field

c) High resistance shunt field and high resistance series field

26) To find the direction of current in a coil you would use

a) Flemmings R/H rule

b) Flemmings L/H rule

c) Corkscrew rule

27) In a transformer, if the rate of change of current is decreased, mutual inductance will

a) Remain the same

b) Increase

c) Decrease

28) If the brake coil in an actuator goes open circuit the actuator will

a) Over ride its mechanical stops

b) Continue to run

c) Stop

29) The speed of a generator with 400Hz supply and 4 poles is

a) 6000 RPM

b) 10000 RPM

c) 12000 RPM

30) An inductance/resistance starter motor is

a) Better than a capacitive

b) More efficient that a capacitive

c) For light loads only

31) The voltage at point C would be equal to

a) 10 V

b) 7V

c) 28V

32) With an output of 200V in a short shunt configuration, the voltage at the series field resistor would be

a) 6 V

b) 10V

c) 450V

33) At point B a voltage in a wire would be

a) Maximum

b) Minimum

c) Zero

34) An ideal 4:1 step down transformer draws 115V and 1A, the output would be

a) 28.5V at 1 A

b) 28.5V at 4 A

c) 460V at 4 A

35) The voltage induced in the stator of an AC generator is produced by

a) A fixed magnetic field

b) A rotating magnetic field

c) An alternating field

36) A low frequency supply

a) May damage inductive circuits

b) Will make the circuit operate faster due to loss of impedance

c) No effect on inductive components

37) A zinc carbon battery life depends on

a) Amount of zinc

b) Purity of carbon

c) Amount of electrolyte paste

38) A batteries terminal voltage at open circuit, with low internal resistance will be

a) Same as the emf

b) Smaller than the emf

c) Greater than the emf

39) When checking the specific gravity of electrolyte in a lead acid battery

a) Check all the cells as they may vary

b) Check the two front cells as they are the terminal cells

c) Check any cell as the will all be the same

40) When a Nickel Cadmium battery is to be stored it should be done

a) Fully charged

b) Fully discharged

c) Totally dry

41) A circuit with a 14.14 peak voltage and a 10W resistance will have a power output of

a) 141.4 W

b) 1.414 W

c) 10 W

42) The power of a piece of equipment with 24V supply with 0.5W resistance and 80A has how much power dissipated?

a) 320 KW

b) 3200 KW

c) 3.2 KW

43) What must you do to make a 3m farad circuit into a 2m farad circuit?

a) Place 1m farad in series

b) Place 3m farads in parallel

c) Place 6m farads in series

44) What does this symbol represent?

a) Light dependent resistor

b) Laser dependent resistor

c) Laser dependent rectifier

45) A parallel circuit at resonance has its impedance at a

a) Maximum

b) Minimum

c) Zero

46) In a capacitive circuit, if frequency is increased

a) Current increases

b) Impedance increases

c) Current decreases

47) If the energy supplied to a circuit for 4hrs 15 mins at 800 j/sec what would be the energy consumed?

a) 3.4 KW Hrs

b) 3400 KW Hrs

c) 340 KW Hrs

48) When switching off the supply, the back emf in a collapsing field in an inductor

a) Never exceeds forward emf

b) Can be multiple times bigger than forward emf

c) Is equal to forward emf

1- The Sine wave signal of a circular time base are:

a-phase separated by 90’

b-phase separated by 180’

c-in phase

2- A Thristor

a-positive temperature coefficient

b-if energized on, will switch on a circuit

c-if energized on, will switch off a circuit

3- What does a Band stop filter do

a-controls certain frequencies within a certain band passing through

b-controls or attenuate all frequencies within a band

4- Motor used in linear actuator is

a-series

b-shunt

c-compound

5- In an AC generator with a supply frequency of 400HZ, it has 4

Poles, what is the RPM?

a-6000RPM

b-9000RPM

c-12000RPM

6- Transformer with star connected primary windings, the secondary Must be

a-star windings

b-Delta windings

c-star or Delta

7- What is the purpose of the capacitor used in a single phase AC

AC motor

a-smoothing

b-changing direction of motor

c-provides a high starting torque

8- The rating of an AC Generator is in

a-KVA

b-KVAR or KW

c-volts and Amps

9- In a vibrating contact voltage regulator the voltage coil is

a-connected in series with the field winding

b-connected in parallel with the field winging

10- in a Delta connected generator the line current is equal to

a-1.7 X phase I

b-1.7 X phase V

11- The voltage rating of a capacitor is

a-the maximum voltage it can take

b-the normal operating voltage

12- The time constant for an 8 micro farad capacitor fitted in a circuit of 1 mega ohms resistor is

a-80 seconds

b-800 mS

c-41 seconds

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Module 3 ii

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13- In a star wound generator, the voltage in a single phase is

a-less than the total of all three phases

b-more than the total of all three phases

c-equal to the total of three phases

14- Generator brush arcing can be caused by

a-brushes located at the neutral axis

b-weak brush spring tension

15- Faradays law

16- Peak voltage is equal to

a-0.707 X maximum voltage

b-0.637 X maximum voltage

c-111.1 X maximum voltage

17- Average voltage is equal to

a-0.707 X maximum voltage

b-0.637 X maximum voltage

c-111.1 X maximum voltage

18- In a Dessyn indicator system, the rotor is

a-permanent magnet

b-electromagnet

19- A low pass filter will have

a- the capacitor in series and resistor in parallel

b- the resistor in series and a capacitor in parallel

c- both resistor and capacitor connected in parallel

20- In an AC generator , to decrease the output voltage

a-decrease RPM or series wound armature current

b-decrease RPM or parallel wound armature current

21- In a series AC resonant circuit

a-the current is maximum at resonant

b-the current is minimum at resonant

c-the impedance is max at resonant

22- In a parallel AC resonant circuit

a-the impedance is minimum at resonance

b-the current is at max at resonance

c-the impedance is maximum at resonance

CAPACITORS

1.What is the time constant for an 8uf capacitor with a 1 Mega ohm resistor?

a. 8 ms

b. 8 seconds*

c. 1 minute

Time to charge = 5x time constant or 5CR were C=Farads & R= Ohms

= 8 seconds 8.800 x 1000 f = 0.008

1Mohm = 1000

Time constant would = 63.2 percent

2. Three capacitors 10 microfarads, 10 nanofarads, 10 milli farads are

connected in parallel. What is there total capacitance?

a. 10,01001 mf *

b. 111 mf

c. 1.001001 mf

Capacitors calculations are opposite to resistors and inductors

So 10mf = 1000000

10nf = 1000

10 mille f = _ _____1

1001001

3. If a 1mf capacitor has a potential difference across it of 5v what is

the energy stored?

a. 12.5 j

b. 12,5 mj *

c. 25 mj

4. A capacitor is fully charged after 25 seconds to a battery voltage of

20v. The battery is replaced with a short circuit. What will be the

Voltage across the capacitor after one time constant?

a. 12.64v

b. 7.36v *

c. 0v

5. A pure capacitor, inductor & resistor are connected in series. The

voltage drop across each is 10v. The total current is 1 amp. How much

power is the current consuming?

a. 30 VA

b. 30 w

c. 10 w *

Capacitor + inductor cancel each other out

VI= Pwr

1 x 10 = 10 w

6. Three 5-microfarad capacitors connected in parallel. What is there

total capacitance?

a. 15 *

b. 5

c. 1.66

Capacitance opposite to resistors and inductors

5+5+5=15

7. The voltage rating of a capacitor is?

a. The max voltage that can be constantly applied *

b. The min voltage required to charge

c. The normal operating voltage

8. When capacitors are joined in parallel the total capacitance is

a. Equal to the sum of the individual capacitors *

b. Less than the smallest of the individual capacitors

c. Dependent on the voltage supplied

9. If the distance between the 2 plates of a capacitor is reduced

what will be the effect?

a capacitance decreases

b capacitance increases *

c capacitance unaffected

10. Relative permitivity dielectric constant is measured with respect to

a space

b dry air

c vacuum *

11. A 50f capacitor is fed with a current of 25 ma. How long will it take to charge it to 100 v?

a. 200 ms *

b. 136 seconds

c. 12 minutes

Q=CV

I= C dV 50 x 0.000001 x 100

dT 25 x 0.0001

V= I dT 5 x 1000 x 0.0001

C 25

V= IT 5

C 25

So T= CV 200ms

I

MAGNETISM

1.Glass is an example of a

a. Paramagnetic material

b. Diamagnetic material *

c. Coercive material

2.The amount of magnetic force left when the magnetising force is

removed is

a. retentivity

b. reminance *

c. resistivity

3. Magnetic dip is least at

a. The poles

b. The equator *

c. The isoclines

4. The point of coercivity occurs when the.

a. Magnetising force applied causes the material to become

magnetically saturated

b Magnetic flux is zero even thought a magnetic force is

being applied. *

c Magnetising force reaches a peak or negative value

5. Flux changes to Field strength changes are

a. Linear

b. Non linear *

c. Linear in opposite direction

6. 2 bar magnets should be stored

a Stuck together to keep their strength

b Separate in a non-magnetic container

c on a magnetic keeper plate *

7. Magnetic wire memory is constructed from

a Ferromagnetic bits

b Ferrite bits *

c. Paramagnetic bits

8. The SI unit for magnetic flux is

a. Flux strength

b. Teslar *

c. F

9. The core material used for an electro magnet is soft iron because

a it demagnetises easily *

b. It demagnetises slowly

c. It has a low reminance

10. The area of a hysteresis loop is proportional to

a The energy absorbed in completely demagnetising the material *

b The saturation point

c The coercive force

11. In a magnetic memory what is information stored on

a. Ferrule beads *

b. Electro magnets

c. Permanent magnets

12. The opposition to magnetic flux is

a. Remanence

b. Reluctance *

c. Resistance

13.What is a collection of ferrite bits used for?

a. Storing numbers

b. Storing a word on a computer*

c. Storing a sentence

14. Ferromagnetic material cannot be magnetised

a. Above a certain temperature *

b Below a certain temperature

c It can always be magnetised

15. Ferrite blocks are used for

a. Permanent magnets

b. Temporary magnets

c. Storing binary numbers *

16. What are the properties of a material suitable for use as

an electromagnet?

a. Low coercivity, high reminance, high permeability

b. Low coercivity, low reminance, high permeability *

c. High coercivity, low reminance, high permeability

17. A paramagnetic material has a relative permeability of

a. Equal to unity

b. Less than unity

c. Greater than unity *

FILTERS

a. What type of filter is shown

a. Band stop

b. Band pass *

c. Low pass

2. What type of filter is shown?

a. Low pass filter

b. Integrator

c. Differentiator *

3. A band stop filter passes signals

a. Outside a range of frequencies *

b. Within a range of frequencies

c. Attenuates outside a range of frequencies

4. A high pass filter has

a. High impedance to low frequency, low impedance to high

frequency *

b. High impedance to high frequency, low impedance to low

frequency

c. High impedance to both low and high frequencies

5. A resistive/capacitive low pass filter will have a

a. Long pulse

b. Short pulse *

c. Equal pulse

AC CIRCUITS

1. What is the current in a parallel ac circuit at resonant frequency?

a. Max

b. Minimum *

c. Zero

2. What is the current in a series ac circuit at resonant frequency?

a. Zero

b. Minimum

c. Max *

3. What is the definition of a coulomb?

a. Amps x seconds *

b. Amps divided by seconds

c. Amps x seconds x coulombs

4. If you apply this waveform to this circuit what is the output

across the capacitor

a. Pulsed positive *

b. Pulsed negative

c. Zero

5. If a capacitor 1uf and an inductor 10mH are connected in

parallel what is their approximate resonant frequency

a. 62Hz

b. 3.2MHz

c. 1.6KHz *

Something wrong with question but equation for calculation is

1

2LC

6. How may the RMS value of an alternating current be defined?

a. The value having the same heating effect as a dc of

equivalent value *

b. The average value having the same heating effect as a dc

of the same value

c. The peak value having the same heating effect as a dc of the

same value

7. What is the relationship between the voltage and a current in a

ac circuit containing resistance and inductance.

a. Current leads voltage by up to 90

b. Current lags voltage by up to 90*

c. Current lags voltage by 90

8. A square wave into an AC circuit with the output across

a capacitor. The output is

a. Saw tooth

b. Pulsating DC

c. Sign wave *

9. The heating effect in an AC circuit is

a. Peak

b. RMS *

c. Average

10. What shape is the waveform when the input pulse and time

base is equal

a. Saw tooth

b. Rectangular

c. Square *

11. A sign wave with 5 amps RMS value has what peak value

a. 7.07amps *

b. 6.37amps

c. 10.00amps

peak value = rms x 1.414

rms = peak value x 0.707

so 5 x 1.414 = 0.707

12. In the diagram

a. Current lags volts by 90

b. Current and volts are in phase

c. Current lags by up to 90*

13. The frequency of a wave with a time period of 1mm second

is

a. 1MHz

b. 1KHz *

c. 1Hz

14. What is the phase difference in a circuit with 100volts and

50amps

a. 90

b. 60*

c. 45

Module 3 iii

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15. What shape is the wave form if the input pulse and time base

are unequal

a. Saw tooth

b. Square

c. Rectangular *

16. What would be the effect on the current in an inductive

circuit if the supply frequency increased

a. The current would increase

b. The current depends on the resistive element of the circuit

c. The current would decrease *

17. Mark to space ratio is written for the following diagram as

a. DE

EF *

b. AC

EF

c. DE

AC

18. At resonant frequency voltage and current are out of phase by

a. Zero degrees *

b. 180 degrees

c. 90 degrees

19. A sinusoidal voltage of 14.14 peak value is connected to a 10 ohm

resistor. The power is

a. 10 watts *

b. 1.414 watts

c. 14.14 watts

14.14 x 0.707 = rms = 9.99698 round up to 10v

v = ir so 10v = I x 10 ohm

I = 1

W = IV so w = 1 x 10v = 10v

20. The frequency of a wave whose time period is 0.5mm seconds

is

a. 1KHz

b. 2KHz *

c. 3KHz

21. The power factor is calculated using which angle of the wave

a. Sine

b. Cos * c. Tan

22. In an AC circuit with no phase lead or lag what is true

a. Real power is zero

b. Real power is greater than apparent power

c. Real power is equal to apparent power *

23. A CRO displays the following waveform. What is the peak

amplitude and frequency

a. 8 volts, 250Hz

b. 4 volts, 1,000 Hz

c. 4 volts, 250 Hz *

24. What happens to the time constant in an AC circuit with the

input through a capacitor

a. Faster

b. Slower *

c. The same

25. In an AC circuit what happens to the inductance if the supply

frequency is reduced

a. Inductance increases to a dangerous level *

b. Circuit becomes resistive

c. Circuit becomes inductive

26. In an inductive circuit

a. Current lags voltage *

b. Voltage lags current

c. Voltage equals current

TRANSFORMERS/INDUCTANCE

1.A transformer with a Y connected primary winding must have a

a. Y secondary winding

b. Delta secondary winding

c. Y or delta secondary winding *

2.A solenoid of 10 turns per Metre carries a current of 5 amps.

If the current were reduced to 2.5 amps how many turns would be

required to maintain the same magnetic field

a. 5

b. 50

c. 20 *

To maintain the same current—turns x amps = amps turns

10 x 5 = 50 so 2.5 x ? = must = 50

2.5 = ? = 20

50

3. What is the mutual inductance if two coils of 10mH and 500mH

have 90% of the flux transferred from one to the other

a. 4.5 milli H

b. 459 milli H

c. 63 milli H *

4. An inductor has 100 turns of wire and a cross sectional area of

0.01m squared. If the core has a permeability of 0.0001 and the

magnetic circuit is 10m what is the value of the inductor

a. 1mH *

b. 100 micro H

c. 100 milli H

0.01 x 0.0001 x 100 = 0.0000100

10

5. Which of these represents absolute permeability

a.*

b.

0

c.

a

6.Three inductors 10 mH, 5mH & 20mH are connected in parallel.

What is there total inductance?

a. 35 milli H

b. 2.86 milli H *

c. You need the coupling factor to calculate it

same as resistors

7. If the current reaches maximum through an inductor of 2 amps

in 5 seconds what is the current after 3 seconds

a. 1.26 amps *

b. 0.63 amps

c. 1 amp

8. A transformer has 200 watts at the primary windings and a

secondary voltage of 400 volts what is the secondary current

a. 2 amps

b. 0.5 amps *

c. 0.05 amps

watts in primary = watts in secondary

w = iv so 200 = ? x 400

200= I = 0.5

400

9. An inductor

a. Smoothes current *

b. Smoothes voltage

c. Smoothes resistance

10. The time constant for an inductor and a resistor is

a. L *

R

b. R

L

c. LR

11. In an inductive transformer if the frequency is doubled

the current will

a. Double

b. Halve *

c. Stay the same

12. a transformer with 1200 primary windings and 4800

secondary windings with 1-kilo ohm in the primary. The

secondary windings would be

a. 1 kilo ohm

b. 2 kilo ohm

c. 4 kilo ohm

ratio = 4800 = 1:4

1200

If 1Kohm in the primary at a ratio of 1:4 secondary must be 4Kohm

13. In an autotransformer

a. Primary coil & secondary coil share some of the windings *

b. Have the same amount of primary & secondary windings

c. Have separate primary & secondary windings

14. Copper loss is due to

a. Voltage flowing in the coil

b. Current flowing in the coil *

c. Capacitance

15. If the rate of change of current in the primary coil of a

transformer is doubled mutual inductance is

a. Doubled

b. Halved *

c. Stays the same

16. To reduce eddy currents in a transformer you would

a. Reduce the thickness of the laminations *

b. Increase the thickness of the laminations

c. Change the dielectric

17. A transformer with 115v primary voltage and a ratio

of 5:1 when a landing light of 24v and 45 amps is used what

is the current drawn.

a. 205 amps

b. 9 amps *

c. 4.5 amps

if 45 amps are in the primary

45 = 9amps

5

18. A transformer has 4500 primary turns of 750 secondary turns

the ratio is

a. 1/6

b. 6:1 *

c. 1:6

19. Two coils at 90to each other the number of flux linkages

are

a. Zero *

b. 2

c.

20. What does the diagram represent?

a. A transformer with 180phase shift between

primary and secondary coils

b. No phase shift between primary and secondary coils *

b. Shows positive and negative terminals

21 The secondary coil of a transformer has 1500 turns and 10 ohms

resistance. The primary has 1 kohm resistance. How many

turns has the primary coil

a. 15.000

b. 150.000 *

c. 1,500.00

1kohm = 1000 ohm so ratio = 1000:10

=100:1

1500 turns at 100:1 = 1500 x 100 = 150000

Generators/Motors

1. In a vibrating contact voltage regulator: -

a. The voltage coil is in series with the field

b. The voltage coil is in parallel with the field *

c. The voltage coil is in parallel with the current coil

2. What is the rating of a generator measured in

a. Kwa

b. Kvar *

c. Kv

3. In a voltage equalising circuit the generators are regulated so

a. The lower output is increased to that of the higher

b. The higher is decreased to that of the lower

c. The lower is increased and the higher is decreased until they

are equal *

4. Decreasing the field current in a shunt motor will do what to

the speed

a. Decrease speed and increase torque

b. Increase speed and increase torque *

c. Increase speed and decrease torque

5. What type of DC motor is used in a linear actuator?

a. Series *

b. Shunt

c. Compound

6. What is the capacitor used for in the diagram?

a. To shift the current

b. To shift the voltage

c. To shift the phase *

7. In a Y wound generator the voltage in a single phase is

a. Less than the total of all 3 *

b. More than the total of all 3

c. Equal to the total of all 3

8. Generator brush arcing is caused by

a. Weak brush springs *

b. Brushes in the neutral plane

c. Interlopes

9. An AC motor that rotates at the same speed as the supply

frequency is

a. A squirrel cage motor

b. A synchronous motor *

c. An AC motor

10. A generator is label as having 115v/200v,20 amps & a power

factor of 0.8.what is the apparent power in each line that the

generator can produce

a. 2.3 Kw

b. 23 Kva

c. 4 Kva *

apparent pwr = IV

200v x 20amps = 4000va = 4kva

11. What is one advantage of using a 3-phase 4 wire star wound

system

a. Two levels of current available

b. Two levels of voltage available *

c. Two levels of voltage and current available

12. From where douse a 3-phase phase squirrel cage induction motor

receive its field

a. DC fed to it via slip rings to a rotating field

b. AC induced into a rotating field on the rotor

c. 3 phase AC supplied to the stator *

13. How is the speed of an induction motor affected by changing the

number of pole pairs

a. Speed will reduce with a reduction in the number of poles

b. Speed will increase with an increase in the number of poles

c. Speed will reduce with an increase in the number of poles *

14.How is the magnetic field in a single-phase induction motor

obtained during starting

a. By supplying dc to the rotating field

b. By using a permanent magnet

c. By splitting the phase with a capacitor *

15.How many cycles of AC are produced in a 6 pole motor for

each rotation

a. 4

b. 3 *

c. 6

16. The neutral plane is the point where

a. The coil is parallel to the magnetic flux

b. The armature windings are cutting the magnetic flux

c. The armature windings are moving parallel to the generator

magnetic flux *

17. If a six pole motor is supplied from a 400Hz source and

rotates at 7800 rpm what is the % slip

a. 1.25%

b. 2.5% *

c. 5.25%

slip = synchronous speed – RPM x 100

synchronous speed

synchronous speed = frequency = number of poles x sync rpm

60

400hz = 3 x ? = 400 x 60 = sync rpm = 8000

60 3

slip = 8000- 7800 x 100 = 2.5

8000

8. How may the power factor be calculated?

a. Kw

Kvar

b. True power

Apparent power *

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19. What current supplies the field of an AC generator?

a. AC

b. DC *

c. AC or DC

20. A two-phase induction motor used in a servomechanism

a. Requires a permanent magnet

b. Is self starting under light loads *

c. Will not self-start

21. If the phase voltage in a star connected generator is 200v what

will be the line voltage

a. 115v

b. 200v

c. 346v *

22. What is true of a 3-phase delta or mesh connected generator

a. Line volts = phase volts. Line current = the 3rd root x phase current *

b. Line current = phase current

3rd root

c. Line voltage = 3rd root x phase voltage

23. Fleming’s left hand rule applies to

a. Generators

b. Motors *

c. Electro magnetic force

24. The current in a DC generator armature is

a. Pulsating DC

b. DC

c. AC *

25. In a 3 phase motor if one phase is lost what happens

a. It runs at two-thirds speed

b. It runs at one-third speed

c. There is on speed difference *

26. The 3 phase currents in a delta wound generator when combined

a. Equal zero *

b. Are out of phase with each other

c. Are in phase with each other

27. On a generator the armature reaction moves the flux

a. In the same direction as the rotation *

a. In the opposite direction as the rotation

c. In the direction of the main flux

28. What is the minimum required number of brushes for

a 4-pole motor

a. 2 *

b. 4

c. 8

29. A split phase starter induction motor after starting

a. Runs as an induction motor *

b. Can only take small loads

c. Runs as a 2-phase motor

30. A 2-phase induction motor will stop when

a. The control phase is reversed

b. The control phase is zero *

c. The control phase is at maximum

31. A 3-phase motor has the windings

a. 120 degrees apart *

b. 90 degrees apart

c. 180 degrees apart

32. An AC generator with 2 pole pairs delivers an output

frequency of 400 Hz. What would the output frequency be if

4 pairs of poles were fitted and the rotational speed remained

the same.

a. 200 Hz

b. 400 Hz

c. 800 Hz *

If 2 poles were upped to 4, speed would normally decrease by half. As speed is to remain the same then the frequency must double

33. Current transformers on the earth neutral of a generator are for

a. Current protection

b. Differential protection *

c. Voltage protection

34. When measuring the phase and line voltage of a generator it

was found that the line voltage was equal to the phase voltage.

The generator is

a. Star wound

b. Delta wound *

c. Compound wound

35. To change the direction of a 3-phase motor you would

a. Change the current direction on the armature

b. Swap over any two of the stator connections *

c. Increase the frequency

36. What values are needed to calculate the generator output?

a. Field strength, frequency and current

b. Field strength and armature speed *

c. Field strength and voltage

37.in a shunt motor what happens if the field current and the

armature current direction are reversed

a. The motor stops

b. The motor reverses

c. The motor continues to run in the same direction *

38. The permanent magnets on a AC generator induces what

a. AC in the exciter field

b. DC in the exciter field *

c. AC in the main field

39. In a single phase to earth neutral of a balanced star wound

generator the phase must be able to

a. Take the maximum load applied to any phase *

b. Current douse not flow between phase and neutral

c. Take the total of all three phases

40. A two-phase induction motor is fed with

a. Phase lead

b. Phase lag *

c. DC

use CIVIL were C=capacitance, I=amps, V=volts and L= inductance

41. A two-phase induction motor has its 2 phases

a. 90 degrees apart *

b. 120 degrees apart

c. 180 degrees apart

42. An AC brush less rotating field alternator is normally

a. Delta wound

b. Star wound *

c. Compound wound

43. Star wound generator line voltage is

a. Equal to phase voltage

b. Root 3 x phase voltage *

c. Root 3 divided by phase voltage

44.one advantage of a starter generator is

a. Although bulkier produces the same power without having

to engage/disengage the drive *

b. The power to weight ratio is improved and the gear is

constantly meshed

c. You get a better start

45. The angular displacement between control coils and

reference coils of a 2-phase induction motor are

a. 90 degrees and 270 degrees *

b. 90 degrees and 180 degrees

c. 90 degrees and 0 degrees

46. To reverse the direction of a 2-phase induction motor

a. You would reverse the polarity of the reference phase

b. You would reverse the polarity of the control phase *

c. You would reverse the polarity of the voltage phase

47. AC motor speed is relative to

a. Voltage

b. Current

c. Number of poles *

48. The stabilizing resistance in the field current of a

generator reacts to

a. Current

b. Voltage

c. Temperature *

49. Calculate the armature current in this DC generator to

the nearest amp

a. 105 amps

b. 100 amps

c. 102 amps *

50. The differential cut out contacts are closed using the

a. Voltage coil *

b. Current coil

c. Voltage and current coil

51. What type of generators are used on aircraft

a. Series

b. Shunt *

c. Compound

52. a shunt wound generator is normally started

a. On load

b. Off load *

c. Either off or on load

53. In a cumulative compound wound generator

a. The series and shunt fields oppose each other

b. The series and shunt fields assist each other *

c. Are no connected

54. The shunt wound generator is controlled by a variable

resistance in

a. Series with the armature

b. In series with the field *

c. Parallel with the armature

55. The separately excited generator voltage is

a. Independent of rotational speed

b. Controlled by the load

c. Controlled by a separate supply *

56. a shunt generator field is supplied by

a. A separate supply

b. The armature *

c. The load

57. A shunt generator voltage falls on load due to

a. High resistance of the field

b. Low resistance of the armature

c. Armature voltage drop *

58. Increasing the speed of a aircraft generator results in

a. Field circuit resistance decrease

b. Field circuit resistance increase *

c. Armature circuit resistance increase

59. Increasing the load on a permanent magnet generator will

a. Reduce terminal voltage by a small amount *

b. Increase terminal voltage by a small amount

c. Have no effect on the terminal voltage

60. The series wound generator terminal voltage will, when

below saturation

a. Increase with an increase in load *

b. Decrease with an increase in load

c. Remain the same with an increase in load

Module 3

1. If the DC generator main contactor is welded closed the fault

would be indicated by

a. The generator failure warning light illuminating -

b. The generator ammeter reading high -

c. The aircraft generator continues to rotate after engine shutdown *

2. The DC generator switch directly controls the

a. Generator field -

b. Generator contactor *

c. Generator warning light -

3. Increasing the load on a permanent magnet generator will

a. Reduce the terminal velocity by a large amount -

b. Reduce the terminal velocity by a small amount *

c. Increase the terminal velocity by a small amount -

4. The separately excited generator voltage is

a. Independent of rotational speed -

b. Controlled by the load -

c. Controlled by a separate supply *

5. The series wound generators terminal voltage will when

below saturation

a. Increase with an increase in load *

b. Decrease with an increase in load -

c. Decrease with a decrease in rotational speed -

6. The shunt wound generator is normally started

a. On load -

b. Off load *

c. Either on or off load -

7. The shunt wound generator is controlled by a variable

resistance in

a. Series with the armature -

b. Series with the field *

c. Parallel with the armature -

8. In a cumulative compound wound generator the

a. Series and shunt fields oppose each other -

b. Series and shunt fields assist each other *

c. Voltage falls suddenly with an increase in load -

9. What type of generators are usually used on aircraft

a. Series -

b. Shunt *

c. Compound -

10. Increasing the speed of an aircraft generator results in an automatic

a. Field circuit resistance increase *

b. Field circuit resistance increase -

c. Armature circuit resistance increase -

Module 3 v

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11. In the shunt generator the field is supplied by

a. a separate supply -

b. The armature *

c. The load -

12. The shunt generators voltage falls on load due to the

a. Height resistance of the field -

b. Low resistance of the armature -

c. Armature volts drop *

13. With a rising generator voltage in a DC generation system the

a. Under volts relay closes before the differential relay *

b. Differential relay closes before the under volts relay -

c. Generator operates normally but the ammeter reads zero -

1. One advantage of using ac electrical power in aircraft is

a: that ac electrical motors can be reversed while dc motors cannot.

b: greater ease in stepping the voltage up or down.

c: that the effective voltage is 1.41 times the maximum instantaneous voltage; therefore, less power input is required.

2. In an ac circuit with no phase lead or lag, which is true?

a: Real power is zero.

b: Real power is greater than apparent power.

c: Real power equals apparent power.

3. The AC power used in most aircraft is:

a. 115Hz

b. 50Hz

c. 400Hz

4. True power in an AC circuit is expressed in terms of:

a. Watts

b. Joules

c. Volt-amps

5. The maximum value of voltage in either the positive or negative direction is known as the:

a. RMS value

b. Peak value

c. Effective value

6. A purely resistive circuit has a power factor of:

a. one

b. two

c. ten

7. As frequency increases, inductive reactance:

a. decreases

b. Increases

c. remains the same

8. In an R - C circuit a change in current will:

a. lead a change in voltage

b. lag a change in voltage

c. does not change due to the presence of the resistor

9. As frequency increases capacitive reactance will:

a. decreases

b. increases

c. remains the same

10. Total reactance in a circuit containing an inductor and a capacitor is:

a. more than the effective d.c. resistance

b. the sum of inductive & capacitive reactance

c. the difference between inductive & capacitive reactance

11. True power in an ac circuit may be found using the formula:

a. P=IV

b. P=I2R

c. P=IVcos

12. The equation for resonant frequency is:

a. 2fc

b.

c.

13. In a series R-L-C circuit at resonant frequency, the current will be at:

a. an undetermined value

b. a maximum value

c. a minimum value

14. In a parallel R-C-L circuit at resonant frequency, the current will be at:

a. an undetermined value

b. a maximum value

c. a minimum value

15. The value of an alternating current measured in terms of the direct current that produces the same heating effect in the same resistance is termed the:

a. root mean square value

b. average value

c. maximum value

16. The peak value of an aircraft 115V single phase a.c. supply is:

a. 81.3V

b. 115V

c. 162.6V

17. The periodic time for an aircraft a.c. supply is:

a. 250mS

b. 25mS

c. 2.5mS

18. The statement that is true is:

a. XL is measured in Henrys’, XC is measured in Farads, Z is measured in.

b. XL and XC are measured in, Z is measured in Impedance

c. XL , XC and Z are all measured in.

19. The current flowing at resonance in a series tuned circuit is:

a.

b.

c.

20. A sinusoidal voltage of 115V at a frequency of 400Hz applied to a coil with negligible resistance, the current is found to be 500mA. The inductance of the coil is:

a. 9.15mH

b. 915mH

c. 91.5mH

21. An aircraft generator is supplying a load of 90kW at a power factor of 0.75 lagging. If the power is raised to unity, how much more power ( in kW ) can the generator supply for the same kilowatt-amp loading:

a. 30kW

b. 120kW

c. 60kW

22. The opposition offered by a coil to the flow of alternating current is called:

a. inductive reactance

b. impedance

c. reluctance

23. An increase in which of the following factors will cause an increase in the inductive reactance of a circuit?

a. voltage

b. resistance

c. frequency

24. An a.c. supply is 115V, 400Hz. Which of the following is false?

a. The periodic time is 2.5mS

b. The rms value of the voltage is 81.3V

c. The peak value of the voltage is 162.61V

25. An alternating voltage is given by v = 200sin(50t-0.30). Which of the following statements is true?

a. The rms voltage is 200V

is leading v = 200 sin50b. The voltage t by 0.30 radians

c. The frequency is 25Hz

26. In an R-C-L series circuit a current of 5A flows when the supply voltage is 100V. The phase angle between the current and voltage is 600 lagging. Which of the following statements is true?

a. The circuit is effectively inductive.

b. The true power is 250W

c. The equivalent circuit reactance is 20.

27. The factors that govern the magnitude of induced emf in a generator are:

a. Flux density, No. of turns on the coil, armature speed, angle at which the lines of force are cut.

b. No. of turns in the armature, flux density, armature speed, angle at which the loops cut the lines of force.

c. Flux density, No. of turns on the coil, field strength, angle at which the lines of force are cut.

28. On an aircraft d.c, generator the pole pieces are:

a. Permanent magnets

b. Electro- magnets

c. Securing devices for the armature

29. In an A/C d.c. generator, armature reaction is compensated for by:

a. Moving the brushes so that they are in the neutral plane when at normal load

b. Using interpoles

c. By " cross magnetising " the generator field

30. The use of interpoles and compensating windings:

a. Increase the life of brushes and commutators

b. Improves efficiency and reduces radio interference

c. Both a and b

31. An aircraft d.c. generator is normally of which class?

a. Permanent magnet excitation

b. Separate excitation

c. Self excitation

32. The most common type of aircraft d.c. generator in

a. Series wound

b. Shunt wound

c. Compound wound

33. In a d.c, generator the purpose of the commutator in to:

a. Pass a current through the armature coils

b. Provide an omni-directional output to the external circuit

c. Provide a unidirectional output to the external circuit

34. An A/C starter generator consists of:

a. One set of field windings and one set of armature windings

b. Two sets of field windings and two sets of armature windings

c. Two sets of field windings and one set of armature windings

35. A starter generator is normally employed on a:

a. Gas turbine engine

b. Reciprocating engine

c. Ground power supply

36. The reason for flashing the field in a generator is to:

a. restore correct polarity and/or residual magnetism to the field poles

b. increase generator capacity

c. remove excess deposits from the commutator and brushes

37. An armature is wound with its coil ends connected to adjacent commutator segments. This configuration is known as:

a. Lap winding

b. Wave winding

c. Overlap winding

38. A Wave wound armature uses:

a. Only two brushes, regardless of the number poles

b. The same number of brushes as poles

c. Multiple parallel paths

39. A lap wound armature is associated with:

a. low voltages and high current machines

b. high voltage and low current machines

c. high voltage and high current machines

40. The unit of capacitance is:

a. the Farad

b. the Henry

c. the Coulomb

41. The amount of charge stored in a capacitor is dependant upon:

a. The gap between the plates, the applied voltage, and the materials used in construction

b. The size of the plates, the gap between the plates and the materials

c. The materials used in construction, the gap between the plates, the size of the plates and the applied voltage

42. 100p farads is equal to:

a. 100 x 1012

b. 100 x 10-12

c. 100 x 10-9

43. The time taken for a capacitor to charge is:

a. 5C

R

b. 5CR

c. rC

R

44. Conventionally, Flemmings left hand rule can be used to determine:

a. the polarity of a solenoid

b. the direction of rotation of a generator

c. the direction of rotation of a motor

45. What magnetic properties do magnets manufactured from soft iron possess?

a. easily magnetised and retains its magnetism

b. easily magnetised but readily demagnetised

c. difficult to magnetise but easily demagnetised

46.Which of the following diagrams shows the correct direction of force on a

current carrying conductor?

47.For a current carrying conductor which of the following field patterns is correct?

48.In the simple d.c. motor illustrated, if the loop of wire is free to rotate it will

do so in:

a. an anticlockwise direction.

b. whichever direction it is given an initial start.

c. a clockwise direction.

49.Materials with narrow hysterisis loops will have:

a. high retentivity

b. low retentivity

c. cannot be magnetised

50.Flux density increases:

a. nonlinearly with MMF

b. linearly with coercive force

c. linearly with MMF

Module 3 vi

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51.The hysterisis loop for a magnetic material is plotted on a graph with:

a. total flux against flux density

b. current against flux density

c. flux density against magnetising force

52.A transformer secondary step-up winding has:

a. more turns than the primary

b. thicker turns than the primary

c. less turns than the primary

53.A capacitor of 0.1 resistor of 1M Ohm are connected inF and a series to a d.c.supply. The time constant of the circuit is:

a. 5S

b. 5mS

c. 5S

54.A transformer with 1,000 turns of primary and 50 turns of secondary winding, if connected to 240V supply would have an output of:

a. 6 volts

b. 12 volts

c. 48 volts

55.A relay whose winding is constructed using many turns of fine wire is essentially a:

a. current coil

b. voltage coil

c. power coil

56. Lenz's Law states:

a. the e.m.f. produced in a circuit is equal to the rate of change of flux

b. the direction of an induced e.m.f. will always oppose the motion that created it

c. the direction of the magnetic flux lines around a wire carrying a current is the same as the direction of the fingers of a right hand point when the wire is held with the thumb pointing in the direction of the conventional current in the wire

57. Magnetic flux density is:

a. the amount of flux per unit area, whose symbol is and the unit is the Tesla ( T ).

b. the amount of flux per unit area, whose symbol is and the unit is the weber (Wb).

c. the number of lines of flux going from the North pole to the South pole.

58.A series AC circuit consisting of an inductor, resistor and a capacitor is connected across an alternating supply. Which of the following statements is true?

a)The voltage across the resistor leads the voltage across the capacitor by 900.

b)The supply voltage leads the circuit current by a given phase angle.

c)The voltage across the capacitor lags the supply voltage by 900.

59.In an AC circuit, the nearer the phase angle between the applied voltage and current is to 0º, the

a) power factor approaches unity

b)apparent power is almost equal to the reactive power.

c)true power is almost equal to the reactive power.

60.At resonance in an L C R circuit, the

a)inductive reactance (XL) is equal to the capacitive reactance (XC).

b)impedance of a series circuit is a maximum.

c)applied voltage is in quadrature to the total circuit current.

61.If, in a 3 phase star connected system, the line voltage is 200v AC, then the phase voltage is

a)is equal to the line voltage x and is approximately equal 115v.

b)measured between any two lines and is equal to 130v.

c)is equal to any line and neutral x and is equal to 115v.

62.To obtain a strong magnetic field in a DC generator, the materials used should be ferromagnetic of

a)High permeability and low reluctance.

b)high retentivity and low permeability.

c)Low permeability and high remanence.

3:12:1:1

63.Armature reaction occurs when the

a)armature magnetic field interacts with the main magnetic field.

b)magnetic neutral axis is in line with the geometric neutral axis.

c)armature magnetic field aids armature rotation.

64.Decreasing the field current of a DC motor will

a)increase the rotational speed.

b)decrease the rotational speed.

c)decrease the output torque.

65.The maximum output voltage from a basic single loop generator is when the loop is

a)cutting maximum lines of magnetic flux.

b)rotating anti-clockwise relative to the direction of the magnetic flux.

c)at 450 to the magnetic flux.

66.When a ferrite core is placed inside a coil, the flux density

a)increases due to the relative permeability of the core.

b)increases due to the increase in magnetising force.

c)decreases due to the increased reluctance of the core.

67.The induced emf in a 20mH coil when a changing current of 20mA/sec is flowing is

a)0.4mV.

b)100mV.

c)400mV.

68.A circuit consists of a coil, battery and switch. When the switch is initially closed, the

a)rate of change of magnetic flux is zero.

b)current rises instantaneously to it’s maximum value.

c)back emf is a maximum.

69.ThreeH are connected inductors of 10mH, 0.01H and 1000 in series. The total value of inductance is approximately

a)11mH.

b)21mH.

c)21H.

70.Prolonged reactive sparking in a DC generator could damage the

a) commutator.

b) armature.

c) pole pieces.

71.If the angular velocity of the armature of an AC generator is approx. 2513 radians/sec, the periodic time of the output voltage is

a)2.5 msecs.

b)25msecs.

c)30 msecs.

72.If the peak to peak value of a sine wave is 10 volts, the RMS value is

a)3.53v.

b)2.45v.

c)8v.

73.A series AC circuit consisting of an inductor, resistor and a capacitor is connected across an alternating supply. Which of the following statements is true?

a)The voltage across the resistor leads the voltage across the capacitor by 900.

b)The supply voltage leads the circuit current by a given phase angle.

c)The voltage across the capacitor lags the supply voltage by 900.

74.A series ac circuit consists of L = 90 mH and R = 40 ohms is connected across a 150v, 50 Hz supply. The approx impedance of the cct is

a)50 ohms.

b)30 ohms.

c)60 ohms.

75.The turns ratio of a transformer used to match the output impedance (1KW) of an amplifier to the input impedance of a loudspeaker (8W) is approximately

a)11: 1 stepdown.

b)8 :1 stepdown.

c)125 : 1 stepdown.

76.If, in a 3 phase star connected system, the line voltage is 200v AC, then the phase voltage is

a)is equal to the line voltage/ Ö3 and is approximately equal 115v.

b)measured between any two lines and is equal to 130v.

c)measured between any line and neutral and is equal to 145v.

77.The power in a delta connected AC system with the line voltage = 115v, line current = 5A and a power factor = 0.85 is approx

a)845W.

b) 490W.

c)1460W.

78.The capacitor that is normally included in the starting circuit of a two phase induction motor fed from an single phase AC supply, is to

a)ensure that the magnetic fields in the main and aux. windings are approx. 90º to each other.

b)to filter out any dc ripple in the supply voltage.

c)build in a time delay in conjunction with the main winding to aid starting.

79.The synchronous speed of an 8 pole AC motor being supplied from 115v 400Hz is

a)6000 RPM.

b)3000 RPM.

c)3200 RPM.

80 The poles of a d.c generator are laminated to:

a. reduce hysterisis losses

b. reduce flux losses

c. reduce eddy current losses

81 Residual voltage is a result of:

a. magnetism in the field windings

b. current flow in the field coils

c. magnetism in the field core

82.In a balanced delta connected 3 phase system, if the phase current is 20A, the

line current is equal to

a)34.64A.

b)20A.

c)56.34A

83.An auto transformer has

a)a single coil, the output winding(s) being tappings on this coil.

b) separate primary and secondary windings.

c) centre tapped primary and secondary windings.

84.The shaded pole motor produces its magnetic fields by

a)By having split pole faces and copper ring on one part of the pole face.

b)shading part of the single phase winding with a capacitor.

c)by causing a 90° phase shift between the poles by including an inductor.

3:15:3:1

85.The poor starting torque of three-phase induction motor can be improved by

a)Increasing the rotor resistance to increase the power factor.

b)decreasing the rotor resistance to decrease the power factor.

c)Increasing the rotor resistance to decrease the power factor.

3:18:2:1

86.A three-phase actuator is often controlled by a change over contactor

a)reversing two of the three-phases allowing it to run in both directions.

b)reversing all three-phases allowing it to operate in both directions.

c)causing a cyclic shift in the stator windings, allowing it to run in both directions.

87. The graph below is a graph of a

a. band stop filter

b. band pass filter

c. high pass filter

3:18:3:1

88. Passive filters are composed entirely of

a. resistors, capacitors and inductors

b. operational amplifiers, resistors and capacitors (not inductors).

c. operational amplifiers, resistors, inductors and capacitors

89. A High pass filter will allow frequencies

a. above a certain value to pass

b. below a certain value to pass

c. within a range to pass

90. What is true of a delta connected generator

a. Line volts = phase volts, line current = phase current.

b. Line current = phase current divided by

c. Line voltage = times phase voltage, Line current = phase current.

91.If a current of 4A exists in a circuit the quantity of charge transferred in 8 seconds is:

a. 12C

b. 2C

c. 32C

92.If an electrical load of 1.5kW is operated for 3 minutes, the energy consumed is:

a. 8.33J

b. 0.27MJ

c. 500J

93.The resistance of a given piece of wire is:

a. Directly proportional to its cross sectional area and inversely proportional to its length.

b. Directly proportional to its length and independent of its cross sectional area.

c. Directly proportional to its length and inversely proportional to its cross sectional area.

95.If an ammeter is connected in a circuit as illustrated it will :

a. have no effect on the circuit.

b. indicate the wrong value.

c. be seriously damaged.

Module 3 vii

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97.A length of resistance wire has to be replaced to obtain a 50% increase in resistance. The new wire, of the same material, should have the same:

(a)diameter and a 50% increase in length

(b)length and a 50% increase in diameter

(c)length and a 50% decrease in diameter.

98. In the figure below. If the volts dropped across the 20 resistor is 10V, the resistance of R1 is:

a. 20

b. 16

c. 2

99.The bridge will be in balance when the value of the unknown resistor R is:

a. 18

b. 14

c. 2

100.A circuit has an applied voltage of 30 volts and a load consisting of a 10ohm resistor in series with a 20ohm resistor. What is the voltage drop across the 10ohm resistor?

a30volts

b20 volts

c10volts

101.Which requires the most electrical power during operation?

A A 12-volt motor requiring 8 amperes.

B Four 30-watt lamps in a 12-volt parallel circuit.

C Two lights requiring 3 amperes each in a 24volt parallel system.

102.A 47K Ohm resistor with a 10% tolerance has the following colour code:

a. Yellow, Violet, Orange, Silver

b. Orange, Violet, Red, Gold

c. Red, Orange, Yellow, Silver

103. A 24volt source is required to furnish 48 watts to a parallel circuit consisting of four resistors of equal value. What is the voltage drop across each resistor?

a. 3V

b. 12V

c. 24V

104.Resistance is defined as:

a. The opposition to the flow of electric charge, irrespective of the temperature

b. The opposition to the flow of electric charge at normal temperatures

c. The time it takes to restrict the voltage in a circuit

105. For how many hours will a 140AH battery deliver 15A.

a. 15.15hours

b. 9.33 hours

c. 27.25 hours

106. What part of a nickel-cadmium cell helps to prevent thermal runaway?

a. The positive plate

b. The negative plate

c. The separator

107. When charging current is applied to a nickel-cadmium battery, the cells emit gas only:

a. toward the end of the charging cycle.

b. when the electrolyte level is low.

c. if the cells are defective.

108. Which of the following can cause thermal runaway in a ni-cad battery:

a. electrical leakage between the cells and the case.

b. excessive current drawn from the battery.

c. charging the battery to more than 100% of its capacity.

109.A Secondary cell is:

a. A cell that is capable of being recharged

b. Not capable of being recharged

c. The primary source of electrical power in an A/C

110.When a battery is to be removed from an aircraft, which lead should be removed first?

a. it makes no difference, provided the master switch is off

b. the lead goings to the main solenoid ( "hot" lead )

c. the lead going to ground

111. A spillage of electrolyte from a Ni-Cad battery is neutralised using:

a.Bicarbonate of soda

b.Warm water

c.Boric acid

112. When a battery is refitted from an aircraft, which lead should be fitted last:

a. Negative

b. Positive

c. It makes no difference, provided the master switch is off.

113.An ammeter in a battery charging system is for the purpose of indicating the

a: amperage available for use.

b: total amperes being used in the aeroplane.

c: rate of current used to charge the battery.

114. In a primary cell sal-ammoniac is:

a. a depolarising agent

b. the electrolyte

c. the annodic material

1. For how many hours will a 140AH battery deliver 15A

2. What part of a nickel Cad cell helps prevent thermal runaway

3. When charging, current is applied to a ni-Cd when do the cells emit gas?

4. What can cause thermal runaway in a Ni-Cd battery

5. What is a secondary cell?

6. When a battery is to be removed from an aircraft which lead should be removed first?

7. A spillage of electrolyte from a Ni Cd battery is neutralised using what?

8. When a battery is refitted to an aircraft which lead should be fitted last?

9. An ammeter in a battery charging system is used to indicate what?

10. In a primary cell what is salammoniac?

11. Reactive power may be found using what formula?

12. How is resistance defined?

13. If an ammeter is connected in parallel in a circuit what will happen to it?

14. High pass frequencies allows what to happen?

15. What are passive filters entirely composed of?

16. What does an auto transformer have?

17. Shaded pole motor produces magnetic fields how?

18. How can poor starting torque of 3 phase induction motor be improved?

19. Residual voltage is a result of what?

20. What is the purpose of laminating the poles of a DC generator?

21. What is damaged by prolonged sparking in a DC generator?

22. What is Lenz’s Law?

23. What is the power in a delta connected AC system with a line voltage of 155V, line current 5A and power factor of 0.85

24. how is Inductive capacitance increased?

25. What does a narrow hystersis loop signify?

26. What does the charge stored on a capacitor depend on?

27. What is the relationship between flux density and MMF?

28. What is the purpose of a capacitor in the starting circuit of a 2 phase inductor motor?

29. In a AC circuit there is a voltage of 115V frequency 400Hz applied to a coil of negligible resistance, the current is 500 mA what is the inductance?

30. What do you know from this: v=200sin(50phixtime - 0.30)

31. What are the use of interpoles and compensating windings?

32. A relay made of many turns of fine wire is what? a) current coil b) voltage coil c)power coil

33. A series circuit containing an inductor, capacitor and resistor across an AC supply which of the following is true:

a) Voltage across resistor leads voltage across capacitor by 90

b) Supply voltage leads current by given phase angle

c) Voltage across capacitor lags supply by 90

34. what is residual voltage the result of?

35. What are the advantages of AC power in an Aircraft?

36. What frequency of AC is used in aircraft?

37. what is true Power measured in?

38. what does the power factor equal in a purely resistive circuit?

39. As the frequency increases what happens to the inductive reactance?

40. As the frequency is increased what happens to the capacitive reactance?

41. In an RC circuit does change in current lead or lag change in voltage?

42. How is the Total reactance of a circuit containing an inductor and capacitor found?

43. How is true power calculated?

44. what is the equation for the resonant frequency?

45. Is the resonant frequency current in a series LCR circuit at it’s Max or min?

46. Is the resonant frequency current in a parallel LCR circuit at it’s Max or min?

47. The value of AC current measured in terms of DC that produces the same heating effect is called what?

48. Peak value of 115V single phase is what?

49. Periodic time of aircraft AC supply is what?

50. The current flowing in series tuned circuit at resonance is found using which formula?

Module 3

________________________________________

JAR 66 Module 3 Questions

1) In a DC motor the stator magnetic field due to armature reaction moves

a) In the sane direction of rotation

b) In the opposite direction to rotation

c) In alignment with GNA

2) A 20 Pico farad capacitor with a 1MW resistor takes how long to charge

a) 20m seconds

b) 1 second

c) 10 seconds

3) Heat exposed to a material will

a) Make all materials harder to magnetise

b) Make all materials easier to magnetise

c) Have no effect on magnetism

4) A transformer has 2000v, 500 turns on the primary and 50 turns on the secondary. What would be the line voltage if the transformer were Delta/Star connected?

a) 200v

b) 346v

c) 450v

5) A transformer to supply a 24v load with a 5:1 turns ratio will have what primary supply?

a) 120v DC

b) 48v AC

c) 120v AC

6) A transformer has 750 primary turns and 4500 secondary, its turns ratio is

a) 6:1

b) 1:6

c) 1/6

7) A band stop filter will

a) Pass all frequencies either side of the band

b) Stop all frequencies either side of the band

c) Stop all frequencies

8) What is this circuit?

a) High Pass Filter

b) Low Pass Filter

c) Band Stop

9) In this circuit, Rx is equal to

a) R3 x R2 ¸ R4

b) R3 x R4 ¸ R2

c) R2 x R3 ¸ R4

10) A parallel circuit with any number of 2 terminal connections

a) Has the same current throughout

b) The sum of the individual voltage drops is equal to the emf

c) The resistance is dependent on current

11) 2 coils, which are turned from being in parallel to 90° but in close proximity, will have its mutual inductance

a) Decreased

b) Remain the same

c) Increase

12) If armature speed is doubled and field strength halved, field strength will

a) Halve

b) Remain the same

c) Double

13) In a circuit with voltage and current which is purely resistive will have its voltage with respect to current

a) In phase

b) 90° Leading

c) 90° Lagging

14) Average value of voltage is equal to

a) 1.1

b) 0.627 x Peak

c) 0.707 x Peak

15) What wave shape is used to control sweep in a CRT?

a) Sine wave

b) Square wave

c) Saw tooth

16) In a 3 phase AC motor, if one phase goes open circuit the motor with a light constant load will

a) Stop

b) Run slowly

c) Run normally

17) Line voltage in a Wye wound transformer is

a) Ö3 ¸ Phase voltage

b) Same as phase voltage

c) Ö3 x Phase voltage

18) To calculate generator output you need to know

a) Armature speed and number of series conductors

b) Field strength and number of armature parallel conductors

c) Series field strength and armature speed

19) What charge does an electron have?

a) Positive

b) No charge

c) Negative

20) An atom, which has gained an electron, will become

a) A negative ion

b) A positive ion

c) A neutral atom

21) An atom, which has few electrons in its valency (less than 4), will have

a) Low resistance

b) High resistance

c) No resistance

22) A 40AH battery will supply 200mA for

a) 250 hrs

b) 40 hrs

c) 200 hrs

23) A 24v, 10 A circuit wit 0.5W resistance will have what power

a) 50W

b) 100W

c) 150W

24) An electrolytic capacitor is used where

a) There is a polarised supply

b) Light loads are used

c) Low frequencies are used

25) A combined starter generator has a

a) Low resistance shunt field and high resistance series field

b) Low resistance series field and high resistance shunt field

c) High resistance shunt field and high resistance series field

26) To find the direction of current in a coil you would use

a) Flemmings R/H rule

b) Flemmings L/H rule

c) Corkscrew rule

27) In a transformer, if the rate of change of current is decreased, mutual inductance will

a) Remain the same

b) Increase

c) Decrease

28) If the brake coil in an actuator goes open circuit the actuator will

a) Over ride its mechanical stops

b) Continue to run

c) Stop

29) The speed of a generator with 400Hz supply and 4 poles is

a) 6000 RPM

b) 10000 RPM

c) 12000 RPM

30) An inductance/resistance starter motor is

a) Better than a capacitive

b) More efficient that a capacitive

c) For light loads only

31) The voltage at point C would be equal to

a) 10 V

b) 7V

c) 28V

32) With an output of 200V in a short shunt configuration, the voltage at the series field resistor would be

a) 6 V

b) 10V

c) 450V

33) At point B a voltage in a wire would be

a) Maximum

b) Minimum

c) Zero

34) An ideal 4:1 step down transformer draws 115V and 1A, the output would be

a) 28.5V at 1 A

b) 28.5V at 4 A

c) 460V at 4 A

35) The voltage induced in the stator of an AC generator is produced by

a) A fixed magnetic field

b) A rotating magnetic field

c) An alternating field

36) A low frequency supply

a) May damage inductive circuits

b) Will make the circuit operate faster due to loss of impedance

c) No effect on inductive components

37) A zinc carbon battery life depends on

a) Amount of zinc

b) Purity of carbon

c) Amount of electrolyte paste

38) A batteries terminal voltage at open circuit, with low internal resistance will be

a) Same as the emf

b) Smaller than the emf

c) Greater than the emf

39) When checking the specific gravity of electrolyte in a lead acid battery

a) Check all the cells as they may vary

b) Check the two front cells as they are the terminal cells

c) Check any cell as the will all be the same

40) When a Nickel Cadmium battery is to be stored it should be done

a) Fully charged

b) Fully discharged

c) Totally dry

41) A circuit with a 14.14 peak voltage and a 10W resistance will have a power output of

a) 141.4 W

b) 1.414 W

c) 10 W

42) The power of a piece of equipment with 24V supply with 0.5W resistance and 80A has how much power dissipated?

a) 320 KW

b) 3200 KW

c) 3.2 KW

43) What must you do to make a 3m farad circuit into a 2m farad circuit?

a) Place 1m farad in series

b) Place 3m farads in parallel

c) Place 6m farads in series

44) What does this symbol represent?

a) Light dependent resistor

b) Laser dependent resistor

c) Laser dependent rectifier

45) A parallel circuit at resonance has its impedance at a

a) Maximum

b) Minimum

c) Zero

46) In a capacitive circuit, if frequency is increased

a) Current increases

b) Impedance increases

c) Current decreases

47) If the energy supplied to a circuit for 4hrs 15 mins at 800 j/sec what would be the energy consumed?

a) 3.4 KW Hrs

b) 3400 KW Hrs

c) 340 KW Hrs

48) When switching off the supply, the back emf in a collapsing field in an inductor

a) Never exceeds forward emf

b) Can be multiple times bigger than forward emf

c) Is equal to forward emf

1- The Sine wave signal of a circular time base are:

a-phase separated by 90’

b-phase separated by 180’

c-in phase

2- A Thristor

a-positive temperature coefficient

b-if energized on, will switch on a circuit

c-if energized on, will switch off a circuit

3- What does a Band stop filter do

a-controls certain frequencies within a certain band passing through

b-controls or attenuate all frequencies within a band

4- Motor used in linear actuator is

a-series

b-shunt

c-compound

5- In an AC generator with a supply frequency of 400HZ, it has 4

Poles, what is the RPM?

a-6000RPM

b-9000RPM

c-12000RPM

6- Transformer with star connected primary windings, the secondary Must be

a-star windings

b-Delta windings

c-star or Delta

7- What is the purpose of the capacitor used in a single phase AC

AC motor

a-smoothing

b-changing direction of motor

c-provides a high starting torque

8- The rating of an AC Generator is in

a-KVA

b-KVAR or KW

c-volts and Amps

9- In a vibrating contact voltage regulator the voltage coil is

a-connected in series with the field winding

b-connected in parallel with the field winging

10- in a Delta connected generator the line current is equal to

a-1.7 X phase I

b-1.7 X phase V

11- The voltage rating of a capacitor is

a-the maximum voltage it can take

b-the normal operating voltage

12- The time constant for an 8 micro farad capacitor fitted in a circuit of 1 mega ohms resistor is

a-80 seconds

b-800 mS

c-41 seconds

13- In a star wound generator, the voltage in a single phase is

a-less than the total of all three phases

b-more than the total of all three phases

c-equal to the total of three phases

14- Generator brush arcing can be caused by

a-brushes located at the neutral axis

b-weak brush spring tension

15- Faradays law

16- Peak voltage is equal to

a-0.707 X maximum voltage

b-0.637 X maximum voltage

c-111.1 X maximum voltage

17- Average voltage is equal to

a-0.707 X maximum voltage

b-0.637 X maximum voltage

c-111.1 X maximum voltage

18- In a Dessyn indicator system, the rotor is

a-permanent magnet

b-electromagnet

19- A low pass filter will have

a- the capacitor in series and resistor in parallel

b- the resistor in series and a capacitor in parallel

c- both resistor and capacitor connected in parallel

20- In an AC generator , to decrease the output voltage

a-decrease RPM or series wound armature current

b-decrease RPM or parallel wound armature current

21- In a series AC resonant circuit

a-the current is maximum at resonant

b-the current is minimum at resonant

c-the impedance is max at resonant

22- In a parallel AC resonant circuit

a-the impedance is minimum at resonance

b-the current is at max at resonance

c-the impedance is maximum at resonance

CAPACITORS

1.What is the time constant for an 8uf capacitor with a 1 Mega ohm resistor?

a. 8 ms

b. 8 seconds*

c. 1 minute

Time to charge = 5x time constant or 5CR were C=Farads & R= Ohms

= 8 seconds 8.800 x 1000 f = 0.008

1Mohm = 1000

Time constant would = 63.2 percent

2. Three capacitors 10 microfarads, 10 nanofarads, 10 milli farads are

connected in parallel. What is there total capacitance?

a. 10,01001 mf *

b. 111 mf

c. 1.001001 mf

Capacitors calculations are opposite to resistors and inductors

So 10mf = 1000000

10nf = 1000

10 mille f = _ _____1

1001001

3. If a 1mf capacitor has a potential difference across it of 5v what is

the energy stored?

a. 12.5 j

b. 12,5 mj *

c. 25 mj

4. A capacitor is fully charged after 25 seconds to a battery voltage of

20v. The battery is replaced with a short circuit. What will be the

Voltage across the capacitor after one time constant?

a. 12.64v

b. 7.36v *

c. 0v

5. A pure capacitor, inductor & resistor are connected in series. The

voltage drop across each is 10v. The total current is 1 amp. How much

power is the current consuming?

a. 30 VA

b. 30 w

c. 10 w *

Capacitor + inductor cancel each other out

VI= Pwr

1 x 10 = 10 w

6. Three 5-microfarad capacitors connected in parallel. What is there

total capacitance?

a. 15 *

b. 5

c. 1.66

Capacitance opposite to resistors and inductors

5+5+5=15

7. The voltage rating of a capacitor is?

a. The max voltage that can be constantly applied *

b. The min voltage required to charge

c. The normal operating voltage

8. When capacitors are joined in parallel the total capacitance is

a. Equal to the sum of the individual capacitors *

b. Less than the smallest of the individual capacitors

c. Dependent on the voltage supplied

9. If the distance between the 2 plates of a capacitor is reduced

what will be the effect?

a capacitance decreases

b capacitance increases *

c capacitance unaffected

10. Relative permitivity dielectric constant is measured with respect to

a space

b dry air

c vacuum *

11. A 50f capacitor is fed with a current of 25 ma. How long will it take to charge it to 100 v?

a. 200 ms *

b. 136 seconds

c. 12 minutes

Q=CV

I= C dV 50 x 0.000001 x 100

dT 25 x 0.0001

V= I dT 5 x 1000 x 0.0001

C 25

V= IT 5

C 25

So T= CV 200ms

I

MAGNETISM

1.Glass is an example of a

a. Paramagnetic material

b. Diamagnetic material *

c. Coercive material

2.The amount of magnetic force left when the magnetising force is

removed is

a. retentivity

b. reminance *

c. resistivity

3. Magnetic dip is least at

a. The poles

b. The equator *

c. The isoclines

4. The point of coercivity occurs when the.

a. Magnetising force applied causes the material to become

magnetically saturated

b Magnetic flux is zero even thought a magnetic force is

being applied. *

c Magnetising force reaches a peak or negative value

5. Flux changes to Field strength changes are

a. Linear

b. Non linear *

c. Linear in opposite direction

6. 2 bar magnets should be stored

a Stuck together to keep their strength

b Separate in a non-magnetic container

c on a magnetic keeper plate *

7. Magnetic wire memory is constructed from

a Ferromagnetic bits

b Ferrite bits *

c. Paramagnetic bits

8. The SI unit for magnetic flux is

a. Flux strength

b. Teslar *

c. F

9. The core material used for an electro magnet is soft iron because

a it demagnetises easily *

b. It demagnetises slowly

c. It has a low reminance

10. The area of a hysteresis loop is proportional to

a The energy absorbed in completely demagnetising the material *

b The saturation point

c The coercive force

11. In a magnetic memory what is information stored on

a. Ferrule beads *

b. Electro magnets

c. Permanent magnets

12. The opposition to magnetic flux is

a. Remanence

b. Reluctance *

c. Resistance

13.What is a collection of ferrite bits used for?

a. Storing numbers

b. Storing a word on a computer*

c. Storing a sentence

14. Ferromagnetic material cannot be magnetised

a. Above a certain temperature *

b Below a certain temperature

c It can always be magnetised

15. Ferrite blocks are used for

a. Permanent magnets

b. Temporary magnets

c. Storing binary numbers *

16. What are the properties of a material suitable for use as

an electromagnet?

a. Low coercivity, high reminance, high permeability

b. Low coercivity, low reminance, high permeability *

c. High coercivity, low reminance, high permeability

17. A paramagnetic material has a relative permeability of

a. Equal to unity

b. Less than unity

c. Greater than unity *

FILTERS

a. What type of filter is shown

a. Band stop

b. Band pass *

c. Low pass

2. What type of filter is shown?

a. Low pass filter

b. Integrator

c. Differentiator *

3. A band stop filter passes signals

a. Outside a range of frequencies *

b. Within a range of frequencies

c. Attenuates outside a range of frequencies

4. A high pass filter has

a. High impedance to low frequency, low impedance to high

frequency *

b. High impedance to high frequency, low impedance to low

frequency

c. High impedance to both low and high frequencies

5. A resistive/capacitive low pass filter will have a

a. Long pulse

b. Short pulse *

c. Equal pulse

AC CIRCUITS

1. What is the current in a parallel ac circuit at resonant frequency?

a. Max

b. Minimum *

c. Zero

2. What is the current in a series ac circuit at resonant frequency?

a. Zero

b. Minimum

c. Max *

3. What is the definition of a coulomb?

a. Amps x seconds *

b. Amps divided by seconds

c. Amps x seconds x coulombs

4. If you apply this waveform to this circuit what is the output

across the capacitor

a. Pulsed positive *

b. Pulsed negative

c. Zero

5. If a capacitor 1uf and an inductor 10mH are connected in

parallel what is their approximate resonant frequency

a. 62Hz

b. 3.2MHz

c. 1.6KHz *

Something wrong with question but equation for calculation is

1

2LC

6. How may the RMS value of an alternating current be defined?

a. The value having the same heating effect as a dc of

equivalent value *

b. The average value having the same heating effect as a dc

of the same value

c. The peak value having the same heating effect as a dc of the

same value

7. What is the relationship between the voltage and a current in a

ac circuit containing resistance and inductance.

a. Current leads voltage by up to 90

b. Current lags voltage by up to 90*

c. Current lags voltage by 90

8. A square wave into an AC circuit with the output across

a capacitor. The output is

a. Saw tooth

b. Pulsating DC

c. Sign wave *

9. The heating effect in an AC circuit is

a. Peak

b. RMS *

c. Average

10. What shape is the waveform when the input pulse and time

base is equal

a. Saw tooth

b. Rectangular

c. Square *

11. A sign wave with 5 amps RMS value has what peak value

a. 7.07amps *

b. 6.37amps

c. 10.00amps

peak value = rms x 1.414

rms = peak value x 0.707

so 5 x 1.414 = 0.707

12. In the diagram

a. Current lags volts by 90

b. Current and volts are in phase

c. Current lags by up to 90*

13. The frequency of a wave with a time period of 1mm second

is

a. 1MHz

b. 1KHz *

c. 1Hz

14. What is the phase difference in a circuit with 100volts and

50amps

a. 90

b. 60*

c. 45

use vector diagram

15. What shape is the wave form if the input pulse and time base

are unequal

a. Saw tooth

b. Square

c. Rectangular *

16. What would be the effect on the current in an inductive

circuit if the supply frequency increased

a. The current would increase

b. The current depends on the resistive element of the circuit

c. The current would decrease *

17. Mark to space ratio is written for the following diagram as

a. DE

EF *

b. AC

EF

c. DE

AC

18. At resonant frequency voltage and current are out of phase by

a. Zero degrees *

b. 180 degrees

c. 90 degrees

19. A sinusoidal voltage of 14.14 peak value is connected to a 10 ohm

resistor. The power is

a. 10 watts *

b. 1.414 watts

c. 14.14 watts

14.14 x 0.707 = rms = 9.99698 round up to 10v

v = ir so 10v = I x 10 ohm

I = 1

W = IV so w = 1 x 10v = 10v

20. The frequency of a wave whose time period is 0.5mm seconds

is

a. 1KHz

b. 2KHz *

c. 3KHz

21. The power factor is calculated using which angle of the wave

a. Sine

b. Cos * c. Tan

22. In an AC circuit with no phase lead or lag what is true

a. Real power is zero

b. Real power is greater than apparent power

c. Real power is equal to apparent power *

23. A CRO displays the following waveform. What is the peak

amplitude and frequency

a. 8 volts, 250Hz

b. 4 volts, 1,000 Hz

c. 4 volts, 250 Hz *

24. What happens to the time constant in an AC circuit with the

input through a capacitor

a. Faster

b. Slower *

c. The same

25. In an AC circuit what happens to the inductance if the supply

frequency is reduced

a. Inductance increases to a dangerous level *

b. Circuit becomes resistive

c. Circuit becomes inductive

26. In an inductive circuit

a. Current lags voltage *

b. Voltage lags current

c. Voltage equals current

TRANSFORMERS/INDUCTANCE

1.A transformer with a Y connected primary winding must have a

a. Y secondary winding

b. Delta secondary winding

c. Y or delta secondary winding *

2.A solenoid of 10 turns per Metre carries a current of 5 amps.

If the current were reduced to 2.5 amps how many turns would be

required to maintain the same magnetic field

a. 5

b. 50

c. 20 *

To maintain the same current—turns x amps = amps turns

10 x 5 = 50 so 2.5 x ? = must = 50

2.5 = ? = 20

50

3. What is the mutual inductance if two coils of 10mH and 500mH

have 90% of the flux transferred from one to the other

a. 4.5 milli H

b. 459 milli H

c. 63 milli H *

4. An inductor has 100 turns of wire and a cross sectional area of

0.01m squared. If the core has a permeability of 0.0001 and the

magnetic circuit is 10m what is the value of the inductor

a. 1mH *

b. 100 micro H

c. 100 milli H

0.01 x 0.0001 x 100 = 0.0000100

10

5. Which of these represents absolute permeability

a.*

b.

0

c.

a

6.Three inductors 10 mH, 5mH & 20mH are connected in parallel.

What is there total inductance?

a. 35 milli H

b. 2.86 milli H *

c. You need the coupling factor to calculate it

same as resistors

7. If the current reaches maximum through an inductor of 2 amps

in 5 seconds what is the current after 3 seconds

a. 1.26 amps *

b. 0.63 amps

c. 1 amp

8. A transformer has 200 watts at the primary windings and a

secondary voltage of 400 volts what is the secondary current

a. 2 amps

b. 0.5 amps *

c. 0.05 amps

watts in primary = watts in secondary

w = iv so 200 = ? x 400

200= I = 0.5

400

9. An inductor

a. Smoothes current *

b. Smoothes voltage

c. Smoothes resistance

10. The time constant for an inductor and a resistor is

a. L *

R

b. R

L

c. LR

11. In an inductive transformer if the frequency is doubled

the current will

a. Double

b. Halve *

c. Stay the same

12. a transformer with 1200 primary windings and 4800

secondary windings with 1-kilo ohm in the primary. The

secondary windings would be

a. 1 kilo ohm

b. 2 kilo ohm

c. 4 kilo ohm

ratio = 4800 = 1:4

1200

If 1Kohm in the primary at a ratio of 1:4 secondary must be 4Kohm

13. In an autotransformer

a. Primary coil & secondary coil share some of the windings *

b. Have the same amount of primary & secondary windings

c. Have separate primary & secondary windings

14. Copper loss is due to

a. Voltage flowing in the coil

b. Current flowing in the coil *

c. Capacitance

15. If the rate of change of current in the primary coil of a

transformer is doubled mutual inductance is

a. Doubled

b. Halved *

c. Stays the same

16. To reduce eddy currents in a transformer you would

a. Reduce the thickness of the laminations *

b. Increase the thickness of the laminations

c. Change the dielectric

17. A transformer with 115v primary voltage and a ratio

of 5:1 when a landing light of 24v and 45 amps is used what

is the current drawn.

a. 205 amps

b. 9 amps *

c. 4.5 amps

if 45 amps are in the primary

45 = 9amps

5

18. A transformer has 4500 primary turns of 750 secondary turns

the ratio is

a. 1/6

b. 6:1 *

c. 1:6

19. Two coils at 90to each other the number of flux linkages

are

a. Zero *

b. 2

c.

20. What does the diagram represent?

a. A transformer with 180 betweenphase shift

primary and secondary coils

b. No phase shift between primary and secondary coils *

b. Shows positive and negative terminals

21 The secondary coil of a transformer has 1500 turns and 10 ohms

resistance. The primary has 1 kohm resistance. How many

turns has the primary coil

a. 15.000

b. 150.000 *

c. 1,500.00

1kohm = 1000 ohm so ratio = 1000:10

=100:1

1500 turns at 100:1 = 1500 x 100 = 150000

Generators/Motors

1. In a vibrating contact voltage regulator: -

a. The voltage coil is in series with the field

b. The voltage coil is in parallel with the field *

c. The voltage coil is in parallel with the current coil

2. What is the rating of a generator measured in

a. Kwa

b. Kvar *

c. Kv

3. In a voltage equalising circuit the generators are regulated so

a. The lower output is increased to that of the higher

b. The higher is decreased to that of the lower

c. The lower is increased and the higher is decreased until they

are equal *

4. Decreasing the field current in a shunt motor will do what to

the speed

a. Decrease speed and increase torque

b. Increase speed and increase torque *

c. Increase speed and decrease torque

5. What type of DC motor is used in a linear actuator?

a. Series *

b. Shunt

c. Compound

6. What is the capacitor used for in the diagram?

a. To shift the current

b. To shift the voltage

c. To shift the phase *

7. In a Y wound generator the voltage in a single phase is

a. Less than the total of all 3 *

b. More than the total of all 3

c. Equal to the total of all 3

8. Generator brush arcing is caused by

a. Weak brush springs *

b. Brushes in the neutral plane

c. Interlopes

9. An AC motor that rotates at the same speed as the supply

frequency is

a. A squirrel cage motor

b. A synchronous motor *

c. An AC motor

10. A generator is label as having 115v/200v,20 amps & a power

factor of 0.8.what is the apparent power in each line that the

generator can produce

a. 2.3 Kw

b. 23 Kva

c. 4 Kva *

apparent pwr = IV

200v x 20amps = 4000va = 4kva

11. What is one advantage of using a 3-phase 4 wire star wound

system

a. Two levels of current available

b. Two levels of voltage available *

c. Two levels of voltage and current available

12. From where douse a 3-phase phase squirrel cage induction motor

receive its field

a. DC fed to it via slip rings to a rotating field

b. AC induced into a rotating field on the rotor

c. 3 phase AC supplied to the stator *

13. How is the speed of an induction motor affected by changing the

number of pole pairs

a. Speed will reduce with a reduction in the number of poles

b. Speed will increase with an increase in the number of poles

c. Speed will reduce with an increase in the number of poles *

14.How is the magnetic field in a single-phase induction motor

obtained during starting

a. By supplying dc to the rotating field

b. By using a permanent magnet

c. By splitting the phase with a capacitor *

15.How many cycles of AC are produced in a 6 pole motor for

each rotation

a. 4

b. 3 *

c. 6

16. The neutral plane is the point where

a. The coil is parallel to the magnetic flux

b. The armature windings are cutting the magnetic flux

c. The armature windings are moving parallel to the generator

magnetic flux *

17. If a six pole motor is supplied from a 400Hz source and

rotates at 7800 rpm what is the % slip

a. 1.25%

b. 2.5% *

c. 5.25%

slip = synchronous speed – RPM x 100

synchronous speed

synchronous speed = frequency = number of poles x sync rpm

60

400hz = 3 x ? = 400 x 60 = sync rpm = 8000

60 3

slip = 8000- 7800 x 100 = 2.5

8000

8. How may the power factor be calculated?

a. Kw

Kvar

b. True power

Apparent power *

c. Watts

Apparent power

19. What current supplies the field of an AC generator?

a. AC

b. DC *

c. AC or DC

20. A two-phase induction motor used in a servomechanism

a. Requires a permanent magnet

b. Is self starting under light loads *

c. Will not self-start

21. If the phase voltage in a star connected generator is 200v what

will be the line voltage

a. 115v

b. 200v

c. 346v *

22. What is true of a 3-phase delta or mesh connected generator

a. Line volts = phase volts. Line current = the 3rd root x phase current *

b. Line current = phase current

3rd root

c. Line voltage = 3rd root x phase voltage

23. Fleming’s left hand rule applies to

a. Generators

b. Motors *

c. Electro magnetic force

24. The current in a DC generator armature is

a. Pulsating DC

b. DC

c. AC *

25. In a 3 phase motor if one phase is lost what happens

a. It runs at two-thirds speed

b. It runs at one-third speed

c. There is on speed difference *

26. The 3 phase currents in a delta wound generator when combined

a. Equal zero *

b. Are out of phase with each other

c. Are in phase with each other

27. On a generator the armature reaction moves the flux

a. In the same direction as the rotation *

a. In the opposite direction as the rotation

c. In the direction of the main flux

28. What is the minimum required number of brushes for

a 4-pole motor

a. 2 *

b. 4

c. 8

29. A split phase starter induction motor after starting

a. Runs as an induction motor *

b. Can only take small loads

c. Runs as a 2-phase motor

30. A 2-phase induction motor will stop when

a. The control phase is reversed

b. The control phase is zero *

c. The control phase is at maximum

31. A 3-phase motor has the windings

a. 120 degrees apart *

b. 90 degrees apart

c. 180 degrees apart

32. An AC generator with 2 pole pairs delivers an output

frequency of 400 Hz. What would the output frequency be if

4 pairs of poles were fitted and the rotational speed remained

the same.

a. 200 Hz

b. 400 Hz

c. 800 Hz *

If 2 poles were upped to 4, speed would normally decrease by half. As speed is to remain the same then the frequency must double

33. Current transformers on the earth neutral of a generator are for

a. Current protection

b. Differential protection *

c. Voltage protection

34. When measuring the phase and line voltage of a generator it

was found that the line voltage was equal to the phase voltage.

The generator is

a. Star wound

b. Delta wound *

c. Compound wound

35. To change the direction of a 3-phase motor you would

a. Change the current direction on the armature

b. Swap over any two of the stator connections *

c. Increase the frequency

36. What values are needed to calculate the generator output?

a. Field strength, frequency and current

b. Field strength and armature speed *

c. Field strength and voltage

37.in a shunt motor what happens if the field current and the

armature current direction are reversed

a. The motor stops

b. The motor reverses

c. The motor continues to run in the same direction *

38. The permanent magnets on a AC generator induces what

a. AC in the exciter field

b. DC in the exciter field *

c. AC in the main field

39. In a single phase to earth neutral of a balanced star wound

generator the phase must be able to

a. Take the maximum load applied to any phase *

b. Current douse not flow between phase and neutral

c. Take the total of all three phases

40. A two-phase induction motor is fed with

a. Phase lead

b. Phase lag *

c. DC

use CIVIL were C=capacitance, I=amps, V=volts and L= inductance

41. A two-phase induction motor has its 2 phases

a. 90 degrees apart *

b. 120 degrees apart

c. 180 degrees apart

42. An AC brush less rotating field alternator is normally

a. Delta wound

b. Star wound *

c. Compound wound

43. Star wound generator line voltage is

a. Equal to phase voltage

b. Root 3 x phase voltage *

c. Root 3 divided by phase voltage

44.one advantage of a starter generator is

a. Although bulkier produces the same power without having

to engage/disengage the drive *

b. The power to weight ratio is improved and the gear is

constantly meshed

c. You get a better start

45. The angular displacement between control coils and

reference coils of a 2-phase induction motor are

a. 90 degrees and 270 degrees *

b. 90 degrees and 180 degrees

c. 90 degrees and 0 degrees

46. To reverse the direction of a 2-phase induction motor

a. You would reverse the polarity of the reference phase

b. You would reverse the polarity of the control phase *

c. You would reverse the polarity of the voltage phase

47. AC motor speed is relative to

a. Voltage

b. Current

c. Number of poles *

48. The stabilizing resistance in the field current of a

generator reacts to

a. Current

b. Voltage

c. Temperature *

49. Calculate the armature current in this DC generator to

the nearest amp

a. 105 amps

b. 100 amps

c. 102 amps *

50. The differential cut out contacts are closed using the

a. Voltage coil *

b. Current coil

c. Voltage and current coil

51. What type of generators are used on aircraft

a. Series

b. Shunt *

c. Compound

52. a shunt wound generator is normally started

a. On load

b. Off load *

c. Either off or on load

53. In a cumulative compound wound generator

a. The series and shunt fields oppose each other

b. The series and shunt fields assist each other *

c. Are no connected

54. The shunt wound generator is controlled by a variable

resistance in

a. Series with the armature

b. In series with the field *

c. Parallel with the armature

55. The separately excited generator voltage is

a. Independent of rotational speed

b. Controlled by the load

c. Controlled by a separate supply *

56. a shunt generator field is supplied by

a. A separate supply

b. The armature *

c. The load

57. A shunt generator voltage falls on load due to

a. High resistance of the field

b. Low resistance of the armature

c. Armature voltage drop *

58. Increasing the speed of a aircraft generator results in

a. Field circuit resistance decrease

b. Field circuit resistance increase *

c. Armature circuit resistance increase

59. Increasing the load on a permanent magnet generator will

a. Reduce terminal voltage by a small amount *

b. Increase terminal voltage by a small amount

c. Have no effect on the terminal voltage

60. The series wound generator terminal voltage will, when

below saturation

a. Increase with an increase in load *

b. Decrease with an increase in load

c. Remain the same with an increase in load

Module 3

1. If the DC generator main contactor is welded closed the fault

would be indicated by

a. The generator failure warning light illuminating -

b. The generator ammeter reading high -

c. The aircraft generator continues to rotate after engine shutdown *

2. The DC generator switch directly controls the

a. Generator field -

b. Generator contactor *

c. Generator warning light -

3. Increasing the load on a permanent magnet generator will

a. Reduce the terminal velocity by a large amount -

b. Reduce the terminal velocity by a small amount *

c. Increase the terminal velocity by a small amount -

4. The separately excited generator voltage is

a. Independent of rotational speed -

b. Controlled by the load -

c. Controlled by a separate supply *

5. The series wound generators terminal voltage will when

below saturation

a. Increase with an increase in load *

b. Decrease with an increase in load -

c. Decrease with a decrease in rotational speed -

6. The shunt wound generator is normally started

a. On load -

b. Off load *

c. Either on or off load -

7. The shunt wound generator is controlled by a variable

resistance in

a. Series with the armature -

b. Series with the field *

c. Parallel with the armature -

8. In a cumulative compound wound generator the

a. Series and shunt fields oppose each other -

b. Series and shunt fields assist each other *

c. Voltage falls suddenly with an increase in load -

9. What type of generators are usually used on aircraft

a. Series -

b. Shunt *

c. Compound -

10. Increasing the speed of an aircraft generator results in an automatic

a. Field circuit resistance increase *

b. Field circuit resistance increase -

c. Armature circuit resistance increase -

11. In the shunt generator the field is supplied by

a. a separate supply -

b. The armature *

c. The load -

12. The shunt generators voltage falls on load due to the

a. Height resistance of the field -

b. Low resistance of the armature -

c. Armature volts drop *

13. With a rising generator voltage in a DC generation system the

a. Under volts relay closes before the differential relay *

b. Differential relay closes before the under volts relay -

c. Generator operates normally but the ammeter reads zero -

1. One advantage of using ac electrical power in aircraft is

a: that ac electrical motors can be reversed while dc motors cannot.

b: greater ease in stepping the voltage up or down.

c: that the effective voltage is 1.41 times the maximum instantaneous voltage; therefore, less power input is required.

2. In an ac circuit with no phase lead or lag, which is true?

a: Real power is zero.

b: Real power is greater than apparent power.

c: Real power equals apparent power.

3. The AC power used in most aircraft is:

a. 115Hz

b. 50Hz

c. 400Hz

4. True power in an AC circuit is expressed in terms of:

a. Watts

b. Joules

c. Volt-amps

5. The maximum value of voltage in either the positive or negative direction is known as the:

a. RMS value

b. Peak value

c. Effective value

6. A purely resistive circuit has a power factor of:

a. one

b. two

c. ten

7. As frequency increases, inductive reactance:

a. decreases

b. Increases

c. remains the same

8. In an R - C circuit a change in current will:

a. lead a change in voltage

b. lag a change in voltage

c. does not change due to the presence of the resistor

9. As frequency increases capacitive reactance will:

a. decreases

b. increases

c. remains the same

10. Total reactance in a circuit containing an inductor and a capacitor is:

a. more than the effective d.c. resistance

b. the sum of inductive & capacitive reactance

c. the difference between inductive & capacitive reactance

11. True power in an ac circuit may be found using the formula:

a. P=IV

b. P=I2R

P=IVcosc.

12. The equation for resonant frequency is:

a. 2fc

b.

c.

13. In a series R-L-C circuit at resonant frequency, the current will be at:

a. an undetermined value

b. a maximum value

c. a minimum value

14. In a parallel R-C-L circuit at resonant frequency, the current will be at:

a. an undetermined value

b. a maximum value

c. a minimum value

15. The value of an alternating current measured in terms of the direct current that produces the same heating effect in the same resistance is termed the:

a. root mean square value

b. average value

c. maximum value

16. The peak value of an aircraft 115V single phase a.c. supply is:

a. 81.3V

b. 115V

c. 162.6V

17. The periodic time for an aircraft a.c. supply is:

a. 250mS

b. 25mS

c. 2.5mS

18. The statement that is true is:

measured in Henrys’, XC is measured in Farads, Z isa. XL is . measured in

XC are measured inb. XL and , Z is measured in Impedance

c. measured inXL , XC and Z are all .

19. The current flowing at resonance in a series tuned circuit is:

a.

b.

c.

20. A sinusoidal voltage of 115V at a frequency of 400Hz applied to a coil with negligible resistance, the current is found to be 500mA. The inductance of the coil is:

a. 9.15mH

b. 915mH

c. 91.5mH

21. An aircraft generator is supplying a load of 90kW at a power factor of 0.75 lagging. If the power is raised to unity, how much more power ( in kW ) can the generator supply for the same kilowatt-amp loading:

a. 30kW

b. 120kW

c. 60kW

22. The opposition offered by a coil to the flow of alternating current is called:

a. inductive reactance

b. impedance

c. reluctance

23. An increase in which of the following factors will cause an increase in the inductive reactance of a circuit?

a. voltage

b. resistance

c. frequency

24. An a.c. supply is 115V, 400Hz. Which of the following is false?

a. The periodic time is 2.5mS

b. The rms value of the voltage is 81.3V

c. The peak value of the voltage is 162.61V

25. An alternating voltage is given by v = t-0.30). Which of the 200sin(50following statements is true?

a. The rms voltage is 200V

b. is leading v = 200 sin50 radiansThe voltage t by 0.30

c. The frequency is 25Hz

26. In an R-C-L series circuit a current of 5A flows when the supply voltage is 100V. The phase angle between the current and voltage is 600 lagging. Which of the following statements is true?

a. The circuit is effectively inductive.

b. The true power is 250W

c. The equivalent circuit reactance. is 20

27. The factors that govern the magnitude of induced emf in a generator are:

a. Flux density, No. of turns on the coil, armature speed, angle at which the lines of force are cut.

b. No. of turns in the armature, flux density, armature speed, angle at which the loops cut the lines of force.

c. Flux density, No. of turns on the coil, field strength, angle at which the lines of force are cut.

28. On an aircraft d.c, generator the pole pieces are:

a. Permanent magnets

b. Electro- magnets

c. Securing devices for the armature

29. In an A/C d.c. generator, armature reaction is compensated for by:

a. Moving the brushes so that they are in the neutral plane when at normal load

b. Using interpoles

c. By " cross magnetising " the generator field

30. The use of interpoles and compensating windings:

a. Increase the life of brushes and commutators

b. Improves efficiency and reduces radio interference

c. Both a and b

31. An aircraft d.c. generator is normally of which class?

a. Permanent magnet excitation

b. Separate excitation

c. Self excitation

32. The most common type of aircraft d.c. generator in

a. Series wound

b. Shunt wound

c. Compound wound

33. In a d.c, generator the purpose of the commutator in to:

a. Pass a current through the armature coils

b. Provide an omni-directional output to the external circuit

c. Provide a unidirectional output to the external circuit

34. An A/C starter generator consists of:

a. One set of field windings and one set of armature windings

b. Two sets of field windings and two sets of armature windings

c. Two sets of field windings and one set of armature windings

35. A starter generator is normally employed on a:

a. Gas turbine engine

b. Reciprocating engine

c. Ground power supply

36. The reason for flashing the field in a generator is to:

a. restore correct polarity and/or residual magnetism to the field poles

b. increase generator capacity

c. remove excess deposits from the commutator and brushes

37. An armature is wound with its coil ends connected to adjacent commutator segments. This configuration is known as:

a. Lap winding

b. Wave winding

c. Overlap winding

38. A Wave wound armature uses:

a. Only two brushes, regardless of the number poles

b. The same number of brushes as poles

c. Multiple parallel paths

39. A lap wound armature is associated with:

a. low voltages and high current machines

b. high voltage and low current machines

c. high voltage and high current machines

40. The unit of capacitance is:

a. the Farad

b. the Henry

c. the Coulomb

41. The amount of charge stored in a capacitor is dependant upon:

a. The gap between the plates, the applied voltage, and the materials used in construction

b. The size of the plates, the gap between the plates and the materials

c. The materials used in construction, the gap between the plates, the size of the plates and the applied voltage

42. 100p farads is equal to:

a. 100 x 1012

b. 100 x 10-12

c. 100 x 10-9

43. The time taken for a capacitor to charge is:

a. 5C

R

b. 5CR

c. rC

R

44. Conventionally, Flemmings left hand rule can be used to determine:

a. the polarity of a solenoid

b. the direction of rotation of a generator

c. the direction of rotation of a motor

45. What magnetic properties do magnets manufactured from soft iron possess?

a. easily magnetised and retains its magnetism

b. easily magnetised but readily demagnetised

c. difficult to magnetise but easily demagnetised

46.Which of the following diagrams shows the correct direction of force on a

current carrying conductor?

47.For a current carrying conductor which of the following field patterns is correct?

48.In the simple d.c. motor illustrated, if the loop of wire is free to rotate it will

do so in:

a. an anticlockwise direction.

b. whichever direction it is given an initial start.

c. a clockwise direction.

49.Materials with narrow hysterisis loops will have:

a. high retentivity

b. low retentivity

c. cannot be magnetised

50.Flux density increases:

a. nonlinearly with MMF

b. linearly with coercive force

c. linearly with MMF

51.The hysterisis loop for a magnetic material is plotted on a graph with:

a. total flux against flux density

b. current against flux density

c. flux density against magnetising force

52.A transformer secondary step-up winding has:

a. more turns than the primary

b. thicker turns than the primary

c. less turns than the primary

F and 53.A capacitor of 0.1 resistor of 1M Ohm are connected in series to aa d.c.supply. The time constant of the circuit is:

a. 5S

b. 5mS

c.S 5

54.A transformer with 1,000 turns of primary and 50 turns of secondary winding, if connected to 240V supply would have an output of:

a. 6 volts

b. 12 volts

c. 48 volts

55.A relay whose winding is constructed using many turns of fine wire is essentially a:

a. current coil

b. voltage coil

c. power coil

56. Lenz's Law states:

a. the e.m.f. produced in a circuit is equal to the rate of change of flux

b. the direction of an induced e.m.f. will always oppose the motion that created it

c. the direction of the magnetic flux lines around a wire carrying a current is the same as the direction of the fingers of a right hand point when the wire is held with the thumb pointing in the direction of the conventional current in the wire

57. Magnetic flux density is:

a. the amount of flux per unit area, whose symbol is and the unit is the Tesla ( T ).

b. the amount of flux per unit area, whose symbol is and the unit is the weber (Wb).

c. the number of lines of flux going from the North pole to the South pole.

58.A series AC circuit consisting of an inductor, resistor and a capacitor is connected across an alternating supply. Which of the following statements is true?

a)The voltage across the resistor leads the voltage across the capacitor by 900.

b)The supply voltage leads the circuit current by a given phase angle.

c)The voltage across the capacitor lags the supply voltage by 900.

59.In an AC circuit, the nearer the phase angle between the applied voltage and current is to 0º, the

a) power factor approaches unity

b)apparent power is almost equal to the reactive power.

c)true power is almost equal to the reactive power.

60.At resonance in an L C R circuit, the

a)inductive reactance (XL) is equal to the capacitive reactance (XC).

b)impedance of a series circuit is a maximum.

c)applied voltage is in quadrature to the total circuit current.

61.If, in a 3 phase star connected system, the line voltage is 200v AC, then the phase voltage is

a)is equal to the line voltage x and is approximately equal 115v.

b)measured between any two lines and is equal to 130v.

c)is equal to any line and neutral x and is equal to 115v.

62.To obtain a strong magnetic field in a DC generator, the materials used should be ferromagnetic of

a)High permeability and low reluctance.

b)high retentivity and low permeability.

c)Low permeability and high remanence.

3:12:1:1

63.Armature reaction occurs when the

a)armature magnetic field interacts with the main magnetic field.

b)magnetic neutral axis is in line with the geometric neutral axis.

c)armature magnetic field aids armature rotation.

64.Decreasing the field current of a DC motor will

a)increase the rotational speed.

b)decrease the rotational speed.

c)decrease the output torque.

65.The maximum output voltage from a basic single loop generator is when the loop is

a)cutting maximum lines of magnetic flux.

b)rotating anti-clockwise relative to the direction of the magnetic flux.

c)at 450 to the magnetic flux.

66.When a ferrite core is placed inside a coil, the flux density

a)increases due to the relative permeability of the core.

b)increases due to the increase in magnetising force.

c)decreases due to the increased reluctance of the core.

67.The induced emf in a 20mH coil when a changing current of 20mA/sec is flowing is

a)0.4mV.

b)100mV.

c)400mV.

68.A circuit consists of a coil, battery and switch. When the switch is initially closed, the

a)rate of change of magnetic flux is zero.

b)current rises instantaneously to it’s maximum value.

c)back emf is a maximum.

69.ThreeH are connected inductors of 10mH, 0.01H and 1000 in series. The total value of inductance is approximately

a)11mH.

b)21mH.

c)21H.

70.Prolonged reactive sparking in a DC generator could damage the

a) commutator.

b) armature.

c) pole pieces.

71.If the angular velocity of the armature of an AC generator is approx. 2513 radians/sec, the periodic time of the output voltage is

a)2.5 msecs.

b)25msecs.

c)30 msecs.

72.If the peak to peak value of a sine wave is 10 volts, the RMS value is

a)3.53v.

b)2.45v.

c)8v.

73.A series AC circuit consisting of an inductor, resistor and a capacitor is connected across an alternating supply. Which of the following statements is true?

a)The voltage across the resistor leads the voltage across the capacitor by 900.

b)The supply voltage leads the circuit current by a given phase angle.

c)The voltage across the capacitor lags the supply voltage by 900.

74.A series ac circuit consists of L = 90 mH and R = 40 ohms is connected across a 150v, 50 Hz supply. The approx impedance of the cct is

a)50 ohms.

b)30 ohms.

c)60 ohms.

75.The turns ratio of a transformer used to match the output impedance (1KW) of an amplifier to the input impedance of a loudspeaker (8W) is approximately

a)11: 1 stepdown.

b)8 :1 stepdown.

c)125 : 1 stepdown.

76.If, in a 3 phase star connected system, the line voltage is 200v AC, then the phase voltage is

a)is equal to the line voltage/ Ö3 and is approximately equal 115v.

b)measured between any two lines and is equal to 130v.

c)measured between any line and neutral and is equal to 145v.

77.The power in a delta connected AC system with the line voltage = 115v, line current = 5A and a power factor = 0.85 is approx

a)845W.

b) 490W.

c)1460W.

78.The capacitor that is normally included in the starting circuit of a two phase induction motor fed from an single phase AC supply, is to

a)ensure that the magnetic fields in the main and aux. windings are approx. 90º to each other.

b)to filter out any dc ripple in the supply voltage.

c)build in a time delay in conjunction with the main winding to aid starting.

79.The synchronous speed of an 8 pole AC motor being supplied from 115v 400Hz is

a)6000 RPM.

b)3000 RPM.

c)3200 RPM.

80 The poles of a d.c generator are laminated to:

a. reduce hysterisis losses

b. reduce flux losses

c. reduce eddy current losses

81 Residual voltage is a result of:

a. magnetism in the field windings

b. current flow in the field coils

c. magnetism in the field core

82.In a balanced delta connected 3 phase system, if the phase current is 20A, the

line current is equal to

a)34.64A.

b)20A.

c)56.34A

83.An auto transformer has

a)a single coil, the output winding(s) being tappings on this coil.

b) separate primary and secondary windings.

c) centre tapped primary and secondary windings.

84.The shaded pole motor produces its magnetic fields by

a)By having split pole faces and copper ring on one part of the pole face.

b)shading part of the single phase winding with a capacitor.

c)by causing a 90° phase shift between the poles by including an inductor.

3:15:3:1

85.The poor starting torque of three-phase induction motor can be improved by

a)Increasing the rotor resistance to increase the power factor.

b)decreasing the rotor resistance to decrease the power factor.

c)Increasing the rotor resistance to decrease the power factor.

3:18:2:1

86.A three-phase actuator is often controlled by a change over contactor

a)reversing two of the three-phases allowing it to run in both directions.

b)reversing all three-phases allowing it to operate in both directions.

c)causing a cyclic shift in the stator windings, allowing it to run in both directions.

87. The graph below is a graph of a

a. band stop filter

b. band pass filter

c. high pass filter

3:18:3:1

88. Passive filters are composed entirely of

a. resistors, capacitors and inductors

b. operational amplifiers, resistors and capacitors (not inductors).

c. operational amplifiers, resistors, inductors and capacitors

89. A High pass filter will allow frequencies

a. above a certain value to pass

b. below a certain value to pass

c. within a range to pass

90. What is true of a delta connected generator

a. Line volts = phase volts, line current = phase current.

b. Line current = phase current divided by

c. Line voltage = times phase voltage, Line current = phase current.

91.If a current of 4A exists in a circuit the quantity of charge transferred in 8 seconds is:

a. 12C

b. 2C

c. 32C

92.If an electrical load of 1.5kW is operated for 3 minutes, the energy consumed is:

a. 8.33J

b. 0.27MJ

c. 500J

93.The resistance of a given piece of wire is:

a. Directly proportional to its cross sectional area and inversely proportional to its length.

b. Directly proportional to its length and independent of its cross sectional area.

c. Directly proportional to its length and inversely proportional to its cross sectional area.

94.In the circuit shown V1 is:

a. 5V

b. 10V

c. 20V

95.If an ammeter is connected in a circuit as illustrated it will :

a. have no effect on the circuit.

b. indicate the wrong value.

c. be seriously damaged.

96. In the circuit shown the current ( IT ) is:

a. 5A

b. 2.5A

c. 80A

97.A length of resistance wire has to be replaced to obtain a 50% increase in resistance. The new wire, of the same material, should have the same:

(a)diameter and a 50% increase in length

(b)length and a 50% increase in diameter

(c)length and a 50% decrease in diameter.

98. In the figure below. If the volts dropped across the 20 resistor is 10V, the resistance of R1 is:

a. 20

b. 16

c. 2

99.The bridge will be in balance when the value of the unknown resistor R is:

a. 18

b. 14

c. 2

100.A circuit has an applied voltage of 30 volts and a load consisting of a 10ohm resistor in series with a 20ohm resistor. What is the voltage drop across the 10ohm resistor?

a30volts

b20 volts

c10volts

101.Which requires the most electrical power during operation?

A A 12-volt motor requiring 8 amperes.

B Four 30-watt lamps in a 12-volt parallel circuit.

C Two lights requiring 3 amperes each in a 24volt parallel system.

102.A 47K Ohm resistor with a 10% tolerance has the following colour code:

a. Yellow, Violet, Orange, Silver

b. Orange, Violet, Red, Gold

c. Red, Orange, Yellow, Silver

103. A 24volt source is required to furnish 48 watts to a parallel circuit consisting of four resistors of equal value. What is the voltage drop across each resistor?

a. 3V

b. 12V

c. 24V

104.Resistance is defined as:

a. The opposition to the flow of electric charge, irrespective of the temperature

b. The opposition to the flow of electric charge at normal temperatures

c. The time it takes to restrict the voltage in a circuit

105. For how many hours will a 140AH battery deliver 15A.

a. 15.15hours

b. 9.33 hours

c. 27.25 hours

106. What part of a nickel-cadmium cell helps to prevent thermal runaway?

a. The positive plate

b. The negative plate

c. The separator

107. When charging current is applied to a nickel-cadmium battery, the cells emit gas only:

a. toward the end of the charging cycle.

b. when the electrolyte level is low.

c. if the cells are defective.

108. Which of the following can cause thermal runaway in a ni-cad battery:

a. electrical leakage between the cells and the case.

b. excessive current drawn from the battery.

c. charging the battery to more than 100% of its capacity.

109.A Secondary cell is:

a. A cell that is capable of being recharged

b. Not capable of being recharged

c. The primary source of electrical power in an A/C

110.When a battery is to be removed from an aircraft, which lead should be removed first?

a. it makes no difference, provided the master switch is off

b. the lead goings to the main solenoid ( "hot" lead )

c. the lead going to ground

111. A spillage of electrolyte from a Ni-Cad battery is neutralised using:

a.Bicarbonate of soda

b.Warm water

c.Boric acid

112. When a battery is refitted from an aircraft, which lead should be fitted last:

a. Negative

b. Positive

c. It makes no difference, provided the master switch is off.

113.An ammeter in a battery charging system is for the purpose of indicating the

a: amperage available for use.

b: total amperes being used in the aeroplane.

c: rate of current used to charge the battery.

114. In a primary cell sal-ammoniac is:

a. a depolarising agent

b. the electrolyte

c. the annodic material

## Sunday, September 27, 2009

### EASA Module 3i MCQ (114 questions)

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