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Module 3 Questions 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 .800 x 1000 f = 0.008= 8 seconds 8 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
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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 f capacitor is
fed with a current of 25 ma. How long will it take to charge50 it
to 100 v? a. 200 ms * b. 136 seconds c. 12 minutes
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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
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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
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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
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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 LC2 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.
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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
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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
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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
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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 currentturns 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
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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 *
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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 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 *
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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
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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
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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
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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. Flemings
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 *
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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 *
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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
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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
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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 *
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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
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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:
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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:
fca. 2 b. c. 13. In a series R-L-C circuit at resonant frequency,
the current will be at:
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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 , Z is
measured in ImpedanceXC are measured in 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
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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 following statements is
true?200sin(50 a. The rms voltage is 200V b. The voltage t by
0.30is leading v = 200 sin50 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
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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:
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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?
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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 a53.A
capacitor of 0.1 resistor of 1M Ohm are connected in series to a
d.c.supply. The time constant of the circuit is: a. 5S b. 5mS Sc. 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:
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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 0, 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.
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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
its maximum value. c)back emf is a maximum. H are connected69.Three
inductors of 10mH, 0.01H and 1000 in series. The total value of
inductance is approximately a)11mH. b)21mH. H.c)21
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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/ 3 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.
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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. 90 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.
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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
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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?
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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.
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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 Lenzs
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?
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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 its Max or min? 46. Is the resonant
frequency current in a parallel LCR circuit at its 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?