electrical engineering Mcqs
1. economics of power generation2. analog electronics3. solid state switching circuits4. parallel circuits5. switchgear and protection6. op amp circuits7. transistor audio power amplifiers8. electrostatics9. heating and welding10. multi stage transistor amplifiers11. passive filters12. network theorems13. regulated d c power supply14. a c fundamentals circuits and circuit theory15. electromagnetic induction16. power electronics17. magnetism and electromagnetism18. transformers19. modulation and demodulation20. d c generators21. semiconductor theory22. single phase induction motors23. semiconductor diode24. hybrid parameters25. digital electronics26. oscillators27. earthing or grounding28. single stage transistor amplifiers29. d c motors30. transistor biasing31. amplifiers with negative feedback32. basic electrical33. electronic instruments34. synchronous motors35. field effect transistors fet36. magnetic circuit37. control systems38. industrial drives39. power generation40. series parallel circuits41. transistor tuned amplifiers42. electrical engineering materials43. rectifiers and converters44. integrated circuits45. scr silicon controlled rectifiers46. cables47. polyphase induction motors48. measurement and instrumentation49. transistors50. electrical machine design51. electrolysis and storage of batteries52. electric traction53. transmission and distribution
4651. Inductors acts as a short circuit for_______________?
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A. AC

B. DC

C. Both A and B

D. none of these

4652. For a purely inductive circuit which of the following is true ?
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A. Apparent power is zero

B. Actual power of the circuit is zero

C. Any capacitance even if present in the circuit will not be charged

D. Relative power is.zero

4653. cmf generated by A.C dynamo depends upon_____________?
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A. number of turns in the coil

B. frequency of rotation

C. magnetic field strength

D. all of above
4654. A coil is wound on iron core which carries current I. The self-induced voltage in the coil is not affected by________________?
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A. variation in coil current

B. variation in voltage to the coil

C. change of number of turns of coil

D. the resistance of magnetic path

4655. The co-efficient of coupling between two air core coils depends on____________?
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A. self-inductance of two coils only

B. mutual inductance and self inductance of two coils

C. mutual inductance between two coils only

D. none of the above

4656. The inductance of a coil will increase under all the following conditions except______________?
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A. when permeability of the core increases

B. when more area for each turn is provided

C. when more length for the same number of turns is provided

D. when the number of turns of the coil increase

4657. If the secondary coil has Ns turns and the primary Np turns the relation between secondary and primary voltages is given by_____________?
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A. Vp/Vs = Ns/Np

B. Vp/Vs = Np/Ns

C. Vs/Vp = Ns/Np

D. Vs/Vp = Np/Ns

4658. Lenzs law is a consequence of the law of conservation of__________?
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A. charge

B. induced e.m.f.

C. induced current

D. energy
4659. Long distance transmission is easy for________________?
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A. Half D.C voltage

B. A.C voltage

C. Half A.C voltage

D. D.C voltage

4660. The average value of the output voltage in a step down dc chopper is given by__________?
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A. V 0 = D V s

B. V 0 = V s

C. V 0 = V s / D

D. V 0 = V s / ( 1 D )

4661. The carrier which are commonly used in constant frequency PWM is______________?
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A. Sawtooth carrier

B. All of these

C. Triangle carrier

D. Inverted sawtooth carrier

4662. The control method used for PWM dc dc converter is______________?
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A. Hysteric control

B. All of these

C. Voltage mode control

D. Current mode control

4663. A rectifier with an external low pass filter is an example of______________?
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A. Direct switch matrix circuits

B. Embedded converters

C. All of these

D. Indirect switch matrix circuits

4664. In a full bridge VSI, in order to avoid the short circuit across the DC bus and the undefined AC output voltage condition, the modulating technique should ensure that___________?
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A. Bottom switch of each leg is on at any instant

B. Top switch of each leg is on at any instant

C. None of these

D. Either A. or B.
4665. Which semiconductor device acts like a diode and two transistor?
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A. UJT

B. Diac

C. SCR

D. Triac
4666. The typical time of rising time lies between______________?
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A. 1 4 s

B. 90 100 s

C. 10 20 s

D. 40 60 s

4667. For a buck converter to reduce the conduction losses in diode
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A. A high on resistance switch can be added in series

B. A low on resistance switch can be added in series

C. A high on resistance switch can be added in parallel

D. A low on resistance switch can be added in parallel

4668. An SCR is considered to be a semi controlled device because_______?
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A. it can be turned OFF but not ON with a gate pulse.

B. it conducts only during one half cycle of an alternating current wave.

C. it can be turned ON but not OFF with a gate pulse.

D. it can be turned ON only during one half cycle of an AC.

4669. How can we protect SCR from thermal conditions _____________?
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A. Using equalizing circuit

B. Use of snubber circuit.

C. Using heat sink.

D. Using CB and fuse.

4670. A crowbar is a circuit which is used to protect a_____________?
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A. voltage sensitive load from excessive dc power supply output voltages

B. current sensitive load from excessive dc power supply output voltages

C. voltage sensitive load from excessive ac power supply output voltages

D. current sensitive load from excessive ac power supply output voltages

4671. In BJT, the forward biased base emitter junction inject holes from base to emitter, the holes_______?
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A. Do not contribute to the collector current

B. Contribute to the collector current

C. Only (b) and (c)

D. Result in net current flow component into the base

E. Only (a) and (b)
4672. The function of snubber circuit connected across the SCR is to___________?
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A. Decrease di / dt.

B. Increase dV / dt.

C. Decrease dV / dt.

D. Suppress dV / dt.
4673. An ideal switch is___________?
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A. Does not carry any current in any direction when it is off

B. All of these

C. Carry current in any direction when it is on

D. Lossless

4674. If a shunt motor is started with its field winding open then?
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A. It will rotate at dangerously high speed

B. It will rotate at the same speed as that with its field winding closed

C. It will rotate at less speed as that with its field winding closed

D. None of these

4675. An SCR has half cycle surge current rating of 3000 A for 50 Hz supply. One cycle surge current will be_____?
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A. 1500 A.

B. 6000 A.

C. 2121.32 A.

D. 4242.64 A.

4676. A TRIAC can be turned on with______________?
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A. Either (a) or (b)

B. None of these

C. Negative voltage at the gate terminal

D. Positive voltage at the gate terminal

4677. Which of the following is used in heat sink_____________?
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A. Carbon

B. Aluminium

C. Iron

D. ilver

4678. The input current waveform of a bridge controlled rectifier when the load is perfectly filtered is___________?
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A. Saw tooth wave

B. Trapezoidal wave

C. Sine wave

D. Square wave
4679. Advantages of Cuk converter is / are_____________?
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A. None of these

B. Low stress on switch

C. Low stress on capacitor

D. Large number of reactive component

4680. Which of the following is disadvantage of fast recovery diodes?
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A. Doping is carried out

B. Recovery is only 50 s

C. Recovery is only 5 s

D. None of these

4681. When a large surge current of very short duration flows through a thyristor then which one of the following device will operate to protect the thyristor ___________?
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A. Snubber circuit

B. Voltage clamping device

C. Fast acting current limiting device (FACL fuse)

D. CB

4682. n a phase controlled 3 phase ac voltage controller, the harmonic present is__________?
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A. 2nd

B. 7th

C. 3rd

D. 5th

4683. Dynamic equalizing circuit is used for________________?
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A. equal division of voltage across each thyristor in parallel

B. equal division of current through each thyristor in parallel

C. equal division of current through each thyristor in series

D. equal division of voltage across each thyristor
4684. Which statement is true ?
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A. Reverse recovery time ( trr ) > gate recovery time (tgr)

B. Device turn OFF time ( tq ) > reverse recover time (trr)

C. All of these

D. Circuit turn OFF time > device turn OFF time ( tq )

4685. Under over voltage condition impedance offered by the voltage clamping device is__________?
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A. moderate

B. low

C. infinity

D. High

4686. A string of n parallel SCRs is operated at 72 KA, the rating of each SCR is 1 KA. If derating factor of the string is 0.1. value of n will be___________?
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A. 60

B. 70

C. 80

D. 90

4687. A combination of synchronized leading edge and trailing edge modulation has also been used to control a____________?
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A. Boost single phase power factor converter

B. A buck dc dc converter to reduce ripple in the intermediate dc bus capacitor

C. Both A. and B.

D. None f these

4688. Which triggering is the most reliable____________?
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A. Thermal triggering

B. Forward voltage triggering

C. Gate triggering

D. dV / dt triggering

4689. Electrical power output in a D.C. generator is equal to_____________?
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A. Mechanical power input iron and friction losses copper losses

B. Electrical power developed in armature iron and copper losses

C. Electrical power developed in armature copper losses

D. Mechanical power input iron and friction losses

4690. The most suited gate pulses given to the AC regulator with R L load can be in the form of____________?
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A. None of these

B. Continuous signal

C. A train of pulses

D. Large isolating pulse transformer

4691. COOLMOS device can be used in application up to power range of___________?
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A. 500 VA

B. 1 KVA

C. 2 KVA

D. 100 KVA

4692. LISN is a device used to measure conducted emissions. LISN stands for_____________?
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A. Line integrated stored network

B. Line impedance stabilization network

C. Line integrated stabilization network

D. Laser integrated stabilization networking

4693. Unipolar modulation is generally used in____________?
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A. DC DC converters

B. AC AC converters

C. AC DC converters

D. DC AC converters

4694. Thyristor is nothing but a____________?
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A. Controlled switch

B. Controlled transistor

C. Amplifier with higher gain

D. Amplifier with large current gain

4695. The reverse recovery time of diode is trr = 3 Is and the rate off all of the diode current is di/dt = 30 A/Is. The storage charge current QRR is___________?
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A. 140 Is

B. 130 Is

C. 135 Is

D. 145 Is

4696. The Graetz bridge makes excellent use of ______________?
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A. SCR

B. Power transformer

C. Potential transformer

D. Current transformer

4697. In constant frequency PWM, at perturbation the amplitude of the sinusoidal component is a___________?
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A. Linear function

B. Non linear function

C. None of these

D. Constant function

4698. In commutation PAC stands for_______?
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A. Phase and commutation

B. Phase angle commutation

C. Phase angle converter

D. Permanent angle converter

4699. A thyristor string is made of a no. of SCR connected in series and parallel. The string have volume and current of 11 KV and 4 KA. The voltage and current rating of available SCRs are 1800 V and 1000 A. For a string efficiency of 90 % let the number of SCRs in series and parallel are a and b respectively. Then the value of a and b will be_____________?
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A. 4, 6

B. 5, 7

C. 7, 5

D. 6, 4

4700. For similar carrier and modulating signals, the line current used in CSI is__________?
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A. Identical to phase voltage in CSI

B. Identical to line current in VSI

C. Identical to line voltage in a VSI

D. Identical to phase voltage in VSI