Electrical fundamentals

Q.1.The effective value of alternating current is calculated by comparing it with1. Resistance 2. Direct current 3. Capacitance 4. AllQ.2.Heat produced by current is proportional to 1. Square of current 2. Square of Resistance 3. Square of capacitance 4. NoneQ.3.The square root of the mean is equal to the1. Effective current 2. Effective Voltage 3. Effective Resistance 4. Effective Power Q.4.The equation of Effective voltage is1. Eff =707xEmax 2. Eff =0.707xEmin 3. Eff =707xEmin 4. Eff =0.707xEmax Q.5.What is frequency1. No of phase per second 2. No of cycles per second 3. No of Oscillation per second 4. NoneQ.6.The meaning of alternation used in alternating current is1. One –complete cycle 2. One –half cycle 3. Two complete cycle 4. NoneQ.7.The Phase angle in electrical equation is usually represented by1. Ω 2.θ 3.π 4.ΨQ.8.Phase angle is the difference in degrees of rotation between1. Two alternating current 2. Two alternating voltage 3. Alternating current & voltage 4. All

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Q.9.In a circuit where current& voltage do not reach Max at the same time then they are said to be 1. Out of phase 2. in phase 3. Null position 4. NoneQ.10.The ability to store electric charge in a capacitor is called1 Inductance 2. Capacitance 3. Reactance 4. NoneQ.11.The capacitance reactance in a circuit is inversely proportional to the 1. Capacitance 2. Capacitance & freq 3. Inductance 4. NoneQ.12.Formula of capacitance reactance is1. Xc = 1/2π fc 2. Xc = 1/2π fL 3. Xc = 1/π fc 4. NoneQ.13.In inductive circuit1. Current leg the voltage 2. Voltage leg the current 3. Current leads the voltage 4. Voltage leads the current Q.14.Inductive reactance in a circuit is1. Inversively of the inductance & freq 2. Proportional to inductance & freq 3. Inversely of the inductance 4. Inversely of the freqQ.15.The formula for inductive reactance is1. XL=2π fL 2. XC=2π fL 3. XL=1/2π fL 4. NoneQ.16.For any circuit that is not purely resistive, the total opposition to current flow is called1. Capacitance 2. Impedance 3. Resistance 4. NoneQ17. One advantage of using Ac electrical power in aircraft is

1. the greater ease in stepping the voltage up or down 2. AC electrical motors can be reversed while dc motors cannot 3. the effective voltage is 1.41 times the maximum instantaneous voltage; therefore, less

power input is required

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Q.18.Power factor is the ratio of1. Apparent power to True power 2. True power to Apparent power3. Alternating current to voltage 4. NoneQ.19.The unit of Power factor is1. KVA 2. KV 3. Joule 4. None Q67. Which of the following is not one of the purposes of interpoles in a generator?

1. Reduce field strength 2. Overcome armature reaction 3. Reduce arcing at the brushes

Q.21.the period of a wave is 1. The same as freq 2. Expressed in ampers3. Time required completing one cycle 4. AllQ.22.Time Period of a sine wave is 1/50 seconds. Its freq is1. 20Hz 2. 30Hz 3. 40Hz 4.50HzQ.23.The RMS value & mean value is same in case of1. Sine wave 2. Triangular wave 3. Square wave 4. None Q.24.For a sine wave of peak value IMAX the RMS value shall be1. 0.5 IMAX

2. 0.707 I MAX 3. 0.91 IMAX 4.1.4141 IMAX

Q.25.The RMS value of a sine wave is 100V. Its peak value shall be1. 70.7 V 2. 141.4 V 3. 150 V 4. None

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Q.26.Power factor of R-C circuit is1. Often zero 2. between 0 & 13. Always 1 4. Between +1 & -1Q.27. True power is the power consumed by the1. Resistance of ac circuit 2. Entire of ac circuit 3. Both 1 & 2 4. NoneQ.28.When Power factor in a circuit is unity, then 1. Phase difference is zero2. Phase difference is 903. Real power is equal to apparent power 4. Both 2 & 3Q.29.For pure inductive (L) or capacitive (c) circuit, the phase shift angle is1.1200

2. 1800 3.2700 4.90 0 Q.30.The power factor of AC circuit is equal to1. Sine of the phase angle 2. Cosine of the phase angle 3. Unity of a resistive circuit 4. NoneQ.31.Unless otherwise specified, any value given for current or voltage in AC circuit is assumed to be 1. Average 2. Effective3. Instaneous4. MaxQ.32.In AC circuit, the ratio of KW to KVA represents1. Form factor 2. Load factor 3. Power factor 4. Diversity factorQ.33.For AC and DC circuits which is correct1. Power is additive 2. Voltage are additive 3. Current are additive 4. None Q.34.Inductive resistance of a circuit increase with increase in1. Resistance & voltage2. Capacitance & voltage 3. Inductance & freq 4. Resistance & freq

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Q.35.Which is true regarding resonance in AC circuit1. At resonance Z=XC 2. At resonance Z=XL 3. At resonance Z= c 4. At resonance Z=R Q.36.When XC=XL in AC circuit, then circuit is said to be1. in correct voltage phase angle 2. in correct current phase angle3. Out of phase4. in resonanceQ.37.In Ac circuit, Voltmeter indicates1. Voltage 2. Effective voltage 3. Effective current 4. Power factorQ.38.The product of volts & Amperes is called1. True power 2. Apparent power 3. Effective voltage 4. NoneQ.39.When capacitance or inductance is in the circuit then1. Current & voltage are not exactly in phase2. Current & voltage are in phase 3. Only 2 is correct 4. NoneQ.40. when capacitance or inductance is in the circuit then1. Apparent power is less than True power 2. True powerless than Apparent power 3. True powerless equal to apparent power 4. NoneQ.41.In any circuit in which there is only resistance, the expression for the relationship of voltage & current is 1. I=E/R2. I=E/XL

3. I=p/R4. NoneQ.42.The symbol of Inductive reactance is1. C 2. R 3. XL 4. L

Q.43.Inductance is measured in1. Ohms2. Farad

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3. Henery 4. None Q.44.The unit used for small air core inductors is1. Ah2. mh 3. None 4. NoneQ.45.When inductors are connected in series then total inductance is given by1. Lt=L1+ L2+ L3+ 2. Lt= 1/ L1+ L2+ L3 3. Only 2 is correct 4. NoneQ.46.In a series resonance circuit, the impedance of the circuit is1. Zero 2. Max3. Min 4. NoneQ.47.Filter circuit is a device which removes1. a.c .components of rectifier O/P but allows the d.c. component to reach the load.2. d.c .components of rectifier O/P but allows the a.c. component to reach the load. 3. Only 2 is correct 4. NoneQ.48.What is the freq of most aircraft AC system 1. 115 Hz2. 220 Hz3. 230 Hz 4. 400 HzQ49. Prolonged reactive sparking in a DC generator could damage the

1. commutator 2. armature3. pole pieces

Q50. The poles of a d.c generator are laminated to

1. reduce hysterisis losses 2. reduce flux losses3. reduce eddy current losses

Q.51.A transformer changes

1. Electrical energy of a given voltage into electrical energy at a different voltage level.

2. Electrical energy of a given voltage into electrical energy at a same voltage level.

3. Mechanical energy of a given voltage into electrical energy at a different voltage level.

4. Mechanical energy of a given voltage into electrical energy at a same voltage level.

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Q53.A transformer consist of

1. Two coils which are electrically connected.

2. Two coils which are not electrically connected .

3. Three coils which are electrically connected

4.Four coils which are not electrically connected

Q.54. The transformer works on the principal of

1. induction effect

2.Mutual induction effect

3.Magnetic effect.

4. Thermocouple effect

Q.55. The transformer can be used with

1. AC current

2.pure dc current

3.pulsating dc current

4.Both 1 & 3

Q.56. The essential parts of a transformer are

1.Primary winding

2. Secondary winding

3.Iron core

4. All

Q.57.in transformer iron core provides

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1. Low reluctance for magnetic lines of force.

2. High reluctance for magnetic lines of force.

3. Low inductance for magnetic lines of force.

4.All

Q58. The windings embedded in the pole faces of a generator are

1. interpoles2. commutating Coils3. compensating Coils

Q.59.In voltage transformer, primary coils are connected in

1. Series across the supply voltage

2.Parellel across the supply voltage

3. Only 2 is correct

4. None

Q60. The windings on a autotransformer are

1. wound on separate legs of core2. wound with the primary over the secondary 3. wound with no magnetic core

Q61. One advantage of using Ac electrical power in aircraft is

1. the greater ease in stepping the voltage up or down 2. AC electrical motors can be reversed while dc motors cannot 3. the effective voltage is 1.41 times the maximum instantaneous voltage; therefore, less power

input is required

Q62. The term used to denote the strength of a magnetic field is

1. retentivity 2. hysterisis 3. flux density

Q63. Which of the following is not one of the purposes of interpoles in a generator?

1. Reduce field strength 2. Overcome armature reaction 3. Reduce arcing at the brushes

Q.64.which transformer is used in instrument circuit.

1.Auto transformer

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2. voltage transformer

3. Current transformer

4. None

Q65.the factor which determines wheather a transformer is a Step-up or Step- down.

1.Current ratio

2. Voltage ratio

3. Turns ratio

4.All

Q66.If transformer is 100 % efficient then

1.the ratio of transformer i/p voltage to o/p voltage is the same as turns ratio.

2. the ratio of transformer i/p voltage to o/p voltage is the differ as turns ratio.

3. the ratio of transformer o/p voltage to i/p voltage is the same as turns ratio.

4. the ratio of transformer o/p voltage to i/p voltage is the differ as turns ratio.

Q67. The difference in speed between a synchronous motor's rotor and stator is known as

1. phase lag2. slip speed 3. rotor lag

Q68.when ac voltage is connected across the primary terminals of transformer, ac current will flow & self induced a voltage in the primary coil which is

1. Same & nearly equal to the applied voltage

2. Opposite & Exact equal to the applied voltage

3. Opposite & nearly equal to the applied voltage

4. None

Q69.If a transformer steps up the voltage, it will

1.step down the current by the same ratio

2.step up the current by the same ratio

3. step down the current by the different ratio

4.step up the current by different ratio

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Q70.Power transformer is used to

1.Step –up voltage

2. Step down voltage

3. Step –up or step down voltage & current

4.None

Q71.Current transformer is a

1.Rectangular – type

2. Ring type

3.cylindrical type

4.square type

Q72.The sides of all current transformers are marked on the unit base.

1.N1 & N2

2.P1 & P2

3.T1 & T2

4. H1 & H2

Q73. Armature reaction causes neutral axis to shift in the direction

1. opposite to the direction of armature rotation2. in the direction of armature rotation 3. either (a) or (b) depending on current flow

Q74.when transformer is not being used but is left in the system then transformer o/p connections should always be connected with a

1.Bonding

2. Simple wire

3. Jumper

4.Fuse

Q75.In a transformer,Copper losss is caused by1.Resistance of conductor comprising turns of coil. 2. Inductance of conductor comprising turns of coil.3. Impedance of conductor comprising turns of coil.4.Current of conductor comprising turns of coil.

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Q76.Wich are the iron losses1. Copper losses 2. Hysteresis losses 3. Eddy current losses 4.Both 2 & 3

Q77. Hysteresis losses is the electrical energy required to 1. Magnitized the primary Winding 2. Magnetized the secondary Winding 3. Magnetized the transformer core 4. None

Q78.Eddy current loss is caused by 1.electric current induced in the transformer core2. electric current induced in the primary winding3. electric current induced in the secondary winding4.None

Q79. Which generators are usually used on aircraft?1. Series 2. Shunt 3. Compound

Q80.The transmission of power over long distances is accomplished by

1.Rectifier

2.Wire

3. Pole

4. Transformer

Q81.transformer for three phase circuit can be connected in any one of several combinations of

1. Y connection 2. Delta connection 3. Both 1 & 2 4. None

Q82.open winding in a transformer can be located by connecting a1.Multimeter 2.Ammeter 3.Voltmeter 4.ohmmeter

Q83. Faradays Law States that 1. the magnitude of the EMF is directly proportional to the rate of change of flux 2. the magnitude of the EMF is indirectly proportional to the rate of change of flux 3. the magnitude of the EMF is directly proportional to the magnetic flux

Q84. A high pass filter will?

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1. allow frequencies above a certain value to pass 2. allow frequencies below a certain value to pass 3. allow frequencies within a range to pass

Q85.What value is the same as the equivalent D.C. heating effect?

1. Root Mean Square 2. Average 3. Peak

Q86. In a 3 phase motor, if 1 phase is lost, the motor

1. remains at the same speed 2. runs at 1 third speed 3. runs at 2 thirds speed

Q87. A three-phase motor has the windings

1. 120° apart 2. 90° apart 3. 180°apart

Q88.A band stop filter

1. stops a narrow range of frequencies 2. stops frequencies either side of a narrow range 3. attenuates frequencies either side of a narrow range

Q89. This is a diagram of a

1. band pass filter 2. high pass filter 3. low pass filter

Q90.Electric motors are often classified according to the method of connecting the field coils and armature. Aircraft engine starter motors are generally of which type

1. compound 2. shunt (parallel) 3. series

Q91. If a heavy mechanical load is removed from a series motor

1. the speed will decrease and the armature current will decrease 2. the speed will increase and the armature current will decrease 3. the speed will increase and the armature current will increase

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Q92. Power is the rate of doing work. It is measured in

1. joules/second 2. watts/second 3. joules x seconds

Q93.One purpose of a growler test is to determine the presence of:

1. a shorted armature 2. an out-of-round commutator 3. a broken field lead

Q94. A step up transformer has

1. one winding 2. two windings

3) three windings

Q95. If a generator sparks, a possible reason is

1. The brush springs are loose 2. The brushes have been placed around the magnetic coil

3) Magnetic flux deflecting the EMF

Q96. In a DC motor the pole pairs are

1. embedded within the field coils 2. part of the armature 3. connected to the brush gear

Q97. A series wound DC motor, the field has

1. few turns of thick wire 2. few turns of thin wire 3. many turns of thin wire

Q98. Starter motors are usually

1. series wound 2. compound wound 3. shunt wound

Q99. How can it be determined if a transformer winding has some of its turns shorted together?

1. measure the input voltage with an ohmmeter 2. the transformer will get hot in normal operation 3. the output voltage will be high

Q100. The voltage output of a generator is controlled by

1. varying the current of the output 2. varying the resistance of the output 3. varying the current of the field

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