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
4551. Which of the following circuit component opposes the change in the circuit voltage ?
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A. Resistance

B. Inductance

C. Conductance

D. Capacitance
4552. In a pure capacitive circuit if the supply frequency is reduced to 1/2, the current will__________?
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A. be reduced by half

B. be reduced to one fourth

C. be four times at high

D. be doubled

4553. In a R-L-C circuit_________?
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A. all above are correct

B. exchange of power takes place between capacitor and supply line

C. exchange of power takes place between inductor and supply line

D. power is consumed in resistance and is equal to I R

E. exchange of power does not take place between resistance and the supply line

4554. Ohm is unit of all of the following except___________?
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A. capacitance

B. resistance

C. capacitive reactance

D. inductive reactance

4555. At _______ frequencies the parallel R-L circuit behaves as purely resistive
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A. low

B. high

C. very high

D. very low

4556. A parallel AC. circuit in resonance will__________?
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A. have current in each section equal to the line current

B. have a high impedance

C. have a high voltage developed across each inductive and capacitive section

D. act like a resistor of low value

4557. Skin effect occurs when a conductor carries current at_______ frequencies
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A. very low

B. medium

C. high

D. low

4558. Which of the following coil will have large resonant frequency __________?
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A. A coil with large distributed capacitance

B. A coil with large resistance

C. A coil with low resistance

D. A coil with low distributed capacitance

4559. The input of an A.C. circuit having power factor of 0.8 lagging is 40 kVA The power drawn by the circuit is__________?
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A. 12 kW

B. 22 kW

C. 64 kW

D. 32 kW
4560. All definitions of power factor of a series R-L-C circuit are correct except__________?
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A. ratio of net reactance and impedance

B. ratio of W and VA

C. ratio of kW and kVA

D. ratio of J and Z

4561. The ratio of active power to apparent power is known as factor__________?
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A. demand

B. power

C. load

D. form

4562. The apparent power drawn by an A.C. circuit is 10 kVA and active power is 8 kW. The reactive power in the circuit is_________?
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A. 8 kVAR

B. 6 kVAR

C. 4 kVAR

D. 16 kVAR

4563. The power factor of a D.C. circuit is always__________?
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A. less than unity

B. zero

C. greater than unity

D. unity
4564. The r.m.s. value of pure cosine function is_________?
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A. 0.707 of peak value

B. zero

C. same as peak value

D. 0.5 of peak value

4565. At very low frequencies a series R-C circuit behaves as almost purely___________?
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A. capacitive

B. inductive

C. resistive

D. none of the above

4566. The series and parallel resonance on L-C circuit differs in that_________?
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A. series resonance needs a high-resistance source for sharp increase in current

B. parallel resonance needs a low-resistance source for a sharp increase in impedance

C. parallel resonance needs a low-resistance source for a sharp rise in line current

D. series resistance needs a low-resistance source for sharp rise in current
4567. In a sine wave the slope is constant_______?
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A. between 180 and 270

B. between 90 and 180

C. between 0 and 90

D. no where
4568. The purpose of a parallel circuit resonance is to magnify________?
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A. frequency

B. power

C. voltage

D. current

4569. The safest value of current the human body can carry for more than 3 second is_________?
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A. 9 mA

B. 15 mA

C. 4 mA

D. 25 mA

4570. In any A.C. circuit always__________?
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A. actual power is more than reactive power

B. reactive power is more than actual power

C. reactive power is more than apparent power

D. apparent power is more than actual power
4571. What will be the phase angle between two alternating waves of equal frequency, when one wave attains maximum value the other is at zero value________ ?
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A. 45

B. 90

C. 0

D. 180

4572. The frequency of domestic power supply in Pakistan is_________?
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A. 200 Hz

B. 50 Hz

C. 60 Hz

D. 100 Hz

4573. If resistance is 20 Q. and inductance is 27 in a R-L series circuit, then time constant of this circuit will be________?
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A. 10 s

B. 100 s

C. 0.001 s

D. 0.1 s
4574. A small coil lies inside a large coil. The two coils are horizontal concentric and carry currents in opposite directions. The large coil will experience______________?
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A. No resultant force

B. A torque about horizontal axis

C. An upward force along the axis

D. A torque about vertical axis

4575. Non inductive resistances are used in decreasing______________?
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A. Self inductance

B. Mutual inductance

C. Magnetic fields

D. Heating effect

4576. An aeroplane of wingspan 10m flies from the equator towards the North Pole. The wings are perpendicular to the vertical component of the earths magnetic field (B = 410-5T). At maximum speed an emf of 96mV is induced across the wing tips. The maximum speed of the aeroplane is____________?
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A. 38.4msec-1

B. 200msec-1

C. 384msec-1

D. 150msec-1

4577. The only difference between construction of D.C generator and A.C generator is that of_______________?
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A. commutator

B. coil

C. carbon brushes

D. magnetic field

4578. A.C and D.C have the same______________?
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A. heating effect through a resistance

B. effect while passing through an inductance

C. effect in charging a capacitor

D. effect in charging a battery

4579. A coil with negligible resistance has 50V across it with 10 mA. The inductive reactance is_____________?
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A. 500 ohms

B. 50 ohms

C. 5000 ohms

D. 1000 ohms

4580. If current in a conductor increases then according to Lenzs law self-induced voltage will____________?
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A. tend to decrease the amount of cur-rent

B. aid the applied voltage

C. produce current opposite to the in-creasing current

D. aid the increasing current

4581. The out put voltage of a transformer is 3 times the input voltage then turns ratio will be________________?
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A. 1

B. 3

C. 3-Jan

D. 6

4582. Which of the following is unit of inductance ?
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A. Webers/metre

B. Ampere turns

C. Ohm

D. Henry
4583. A metal rod of 25 cm length is moving at a speed of 0.5/sec in direction perpendicular to 0.25T magnetic field. Emf produced in the rod is_____________?
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A. 0.03125 volt

B. 0 volt

C. 31.25 volt

D. 3.125 volt

4584. A coil of wire is arranged with its plane perpendicular to a uniform magnetic field o flux density B. when the radius of the coil increases from r1 to r2 in time ?t then what is the emf induced in the coil ?
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A. ?B(r2-r1)2/?t

B. ?B/r22-r12/?t

C. ?B(r22+r12)/?t

D. ?B(r22-r12)/?t
4585. The property of coil by which a counter e.m.f. is induced in it when the current through the coil changes is known as__________?
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A. capacitance

B. series aiding inductance

C. mutual inductance

D. self-inductance
4586. Which circuit element(s) will oppose the change in circuit current ?
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A. Capacitance only

B. Inductance only

C. Resistance only

D. Inductance and capacitance

4587. A.C cannot be used for________________?
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A. producing light

B. producing heat

C. magnetizing and electroplating

D. all the above

4588. The core of a coil has a length of 200 mm. The inductance of coil is 6 mH. If the core length is doubled, all other quantities, remaining the same, the inductance will be_____________?
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A. 48mH

B. 24mH

C. 12 mH

D. 3 mH
4589. Current produced by moving the loop of wire across a magnetic field is called_____________?
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A. mean square current

B. A.C current

C. D.C current

D. induced current
4590. Which of the fpllowing inductor will have the least eddy current losses ?
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A. Powdered iron core

B. Laminated iron core

C. Iron core

D. Air core
4591. Two 300 uH coils in series without mutual coupling have a total inductance of___________?
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A. 150 uH

B. 300 uH

C. 600 uH

D. 75 uH

4592. Which one of the following devices does not function like an electric motor ?
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A. Voltmeter

B. Ammeter

C. Transformer

D. Galvanometer

4593. The self-inductance of a solenoid is increased when a soft iron core is inserted into it. This is because the soft iron core_______________?
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A. Reduces the effect of eddy current

B. Increases the mutual inductance between the solenoid and the core

C. Improves the flux linkage between the turns of the coil

D. Decreases the resistance of the solenoid

4594. Magnetic compass needle will be deflecting if it is kept near________________?
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A. Accelerating charge

B. Soft iron

C. Static charge

D. Semi-conductor

4595. Transformer works on the principle of________________?
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A. Law of conservation of power

B. Mutual induction

C. Lenzs law

D. Faradays law

4596. When the motor is at its maximum speed then back emf will be______________?
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A. Zero

B. Maximum

C. No back emf

D. Intermediate values

4597. Find the force acting on a conductor 3m long carrying a current of 50 amperes at right angles to a magnetic field having a flux density of 0.67 tesla
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A. 1000 N

B. 600 N

C. 400 N

D. 100 N
4598. A crack in the magnetic path of an inductor will result in________________?
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A. reduced inductance

B. zero inductance

C. increased inductance

D. unchanged inductance

4599. In case of an inductance, current is proportional to___________?
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A. voltage across the inductance

B. magnetic field

C. both A. and B.

D. neither (A) nor (B)

4600. The magnitude of the induced e.m.f. in a conductor depends on the______________?
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A. flux density of the magnetic field

B. amount of flux linkages

C. rate of change of flux-linkages

D. amount of flux cut