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D.C. Motors

Study 130 Electrical Engineering MCQs with correct answers and explanations.

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41Electrical EngineeringMedium

D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this________?

Ashunt motor

Bseries motor

Ccompound motor

Dany of the above

Correct answer

C. compound motor

Explanation

The correct answer is compound motor.

42Electrical EngineeringMedium

Why are the D.C. motors preferred for traction applications?

AThe speed is inversely proportional to the torque and the torque is proportional to square of armature current

BTorque is proportional to armature current

CTorque and speed are inversely proportional to armature current

DTorque is proportional to square root of armature current

Correct answer

A. The speed is inversely proportional to the torque and the torque is proportional to square of armature current

Explanation

The correct answer is The speed is inversely proportional to the torque and the torque is proportional to square of armature current.

43Electrical EngineeringMedium

If the supply voltage for a D.C. motor is increased, which of the following will decrease?

AAll of the above

BFull-load current

CStarting torque

DOperating speed

Correct answer

B. Full-load current

Explanation

The correct answer is Full-load current.

44Electrical EngineeringMedium

Which motor has the poorest speed control?

ACumulatively compounded motor

BShunt motor

CSeries motor

DDifferentially compounded motor

Correct answer

C. Series motor

Explanation

The correct answer is Series motor.

45Electrical EngineeringMedium

Armature reaction in dc motor results________?

Adecrease in speed

Bopen circuit

Cshort circuit

Dincrease in speed

Correct answer

D. increase in speed

Explanation

The correct answer is increase in speed.

46Electrical EngineeringMedium

The ratio of starting torque to full-load torque is least in case of________?

Acompound motors

Bshunt motors

Cseries motors

Dnone of the above

Correct answer

B. shunt motors

Explanation

The correct answer is shunt motors.

47Electrical EngineeringMedium

Which D.C. motor is generally preferred for cranes and hoists?

AShunt motor

BDifferentially compounded motor

CCumulatively compounded motor

DSeries motor

Correct answer

D. Series motor

Explanation

The correct answer is Series motor.

48Electrical EngineeringMedium

D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the________?

Ashunt motor

Bany of the above

Ccompound motor

Dseries motor

Correct answer

D. series motor

Explanation

The correct answer is series motor.

49Electrical EngineeringMedium

Which method of braking is generally used in elevators?

ARegenerative braking

BRheostatic braking

CNone of the above

DPlugging

Correct answer

D. Plugging

Explanation

The correct answer is Plugging.

50Electrical EngineeringMedium

In a D.C. generator all of the following could be the effects of iron losses except________?

ARise in temperature of ventilating air

BIncrease in terminal voltage

CExcessive heating of core

DLoss of efficiency

Correct answer

B. Increase in terminal voltage

Explanation

The correct answer is Increase in terminal voltage.

Why are the D.C. motors preferred for traction applications?

AThe speed is inversely proportional to the torque and the torque is proportional to square of armature current

BTorque is proportional to armature current

CTorque and speed are inversely proportional to armature current

DTorque is proportional to square root of armature current

Correct answer

A. The speed is inversely proportional to the torque and the torque is proportional to square of armature current

Explanation

The correct answer is The speed is inversely proportional to the torque and the torque is proportional to square of armature current.