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D.C. Motors

Study 130 Electrical Engineering MCQs with correct answers and explanations.

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111Electrical EngineeringMedium

D.C. generators are installed near the load centres to reduce________?

Aline losses

Biron losses

Csparking

Dcorona losses

Correct answer

A. line losses

Explanation

The correct answer is line losses.

112Electrical EngineeringMedium

Sparking, is discouraged in a D.C. motor because________?

Ait increases the input power con-sumption

Bnone of the above

Ccommutator gets damaged

Dboth A. and B.

Correct answer

C. commutator gets damaged

Explanation

The correct answer is commutator gets damaged.

113Electrical EngineeringMedium

By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?

AShaft

BCommutator

CStator

DFrame

Correct answer

B. Commutator

Explanation

The correct answer is Commutator.

114Electrical EngineeringMedium

In case of D.C. shunt motors the speed is dependent on back e.m.f. only because________?

Aback e.m.f. is equal to armature drop

Bflux is practically constant in D:C. shunt motors

Cflux is proportional to armature current

Darmature drop is negligible

Correct answer

B. flux is practically constant in D:C. shunt motors

Explanation

The correct answer is flux is practically constant in D:C. shunt motors.

115Electrical EngineeringMedium

The direction of rotation of a D.C. series motor can be changed by________?

Ainterchanging field terminals

BNone of the above

Cinterchanging supply terminals

Deither of A. and B. above

Correct answer

A. interchanging field terminals

Explanation

The correct answer is interchanging field terminals.

116Electrical EngineeringMedium

Which of the following motors one will choose to drive the rotary compressor?

AD.C. series motor

BD.C. shunt motor

CUniversal motor

DSynchronous motor

Correct answer

D. Synchronous motor

Explanation

The correct answer is Synchronous motor.

117Electrical EngineeringMedium

If I2 be the armature current, then speed of a D.C. shunt motor is________?

Avaries as la

Bproportional to la

Cindependent of Ia

Dvaries as (Ia)

Correct answer

C. independent of Ia

Explanation

The correct answer is independent of Ia.

118Electrical EngineeringMedium

The type of D.C. motor used for shears and punches is________?

Adifferential compoutid D.C. motor

Bshunt motor

Cseries motor

Dcumulative compound D.C. motor

Correct answer

D. cumulative compound D.C. motor

Explanation

The correct answer is cumulative compound D.C. motor.

119Electrical EngineeringMedium

Which one of the following is not the function of pole shoes in a D.C. machine?

ATo support the field coils

BTo spread out flux for better uniformity

CTo reduce the reluctance of the magnetic path

DTo reduce eddy current loss

Correct answer

D. To reduce eddy current loss

Explanation

The correct answer is To reduce eddy current loss.

120Electrical EngineeringMedium

One D.C. motor drives another D.C. motor. The second D.C. motor when excited and driven________?

Aruns as a generator

Balso runs as a motor comes to stop after sometime

Cdoes not run as a generator

Correct answer

A. runs as a generator

Explanation

The correct answer is runs as a generator.

In case of D.C. shunt motors the speed is dependent on back e.m.f. only because________?

Aback e.m.f. is equal to armature drop

Bflux is practically constant in D:C. shunt motors

Cflux is proportional to armature current

Darmature drop is negligible

Correct answer

B. flux is practically constant in D:C. shunt motors

Explanation

The correct answer is flux is practically constant in D:C. shunt motors.