Explore topic-wise MCQs in Dc Machines.

This section includes 15 Mcqs, each offering curated multiple-choice questions to sharpen your Dc Machines knowledge and support exam preparation. Choose a topic below to get started.

1.

WHICH_OF_THE_FOLLOWING_QUANTITY_WILL_DECREASE_IF_SUPPLY_VOLTAGE_IS_INCREASED??$

A. Starting torque
B. Operating speed
C. Full-load current
D. Cannot be determined
Answer» D. Cannot be determined
Discussion
2.

Sometimes motor has to be de-rated.$

A. True
B. False
Answer» B. False
Discussion
3.

In which of the following case we will get maximum power?$

A. E<sub>a</sub> = 2 x supply voltage
B. E<sub>a</sub> = supply voltage
C. Supply voltage = 2 x E<sub>a</sub>
D. supply voltage = 4 x E<sub>a</sub>
Answer» D. supply voltage = 4 x E<sub>a</sub>
Discussion
4.

Sparking is discouraged in a DC motor.

A. True
B. False
Answer» C.
Discussion
5.

In DC machines the residual magnetism is present. The order of residual magnetism is ___________

A. 2 to 3 per cent
B. 10 to 15 per cent
C. 20 to 25 per cent
D. 50 to 75 per cent
Answer» B. 10 to 15 per cent
Discussion
6.

The armature shaft of a DC motor must be able to withstand ______________

A. Bending moment due to weight of the armature.
B. Any unbalanced magnetic pull on the armature core.
C. Twisting stains due to transmission of torque.
D. Bending moment, unbalanced magnetic pull and twisting stains
Answer» E.
Discussion
7.

An electric motor is having constant output power. So, motor will have a torque speed characteristic ______________________?

A. Circle about the origin.
B. Straight line parallel to the speed axis.
C. Straight line through the origin.
D. Rectangular hyperbola
Answer» E.
Discussion
8.

Which power is mentioned on a name plate of a motor?

A. Gross power
B. Power drawn in kVA
C. Power drawn in kW
D. Output power available at the shaft
Answer» E.
Discussion
9.

The current drawn by the armature of DC motor is directly proportional to ________________

A. Torque
B. Speed
C. The voltage across the terminals
D. Cannot be determined
Answer» B. Speed
Discussion
10.

Direction of rotation of motor is determined by ____________

A. Faraday’s law
B. Lenz’s law
C. Coulomb’s law
D. Fleming’s left-hand rule
Answer» E.
Discussion
11.

In DC motor, which of the following part can sustain the maximum temperature rise?

A. Field winding
B. Commutator
C. Slip rings
D. Armature winding
Answer» B. Commutator
Discussion
12.

Which part will surely tell that given motor is DC motor and not an AC type?

A. Winding
B. Shaft
C. Commutator
D. Stator
Answer» D. Stator
Discussion
13.

What will happen, with the increase in speed of a DC motor?

A. Back emf increase but line current falls.
B. Back emf falls and line current increase.
C. Both back emf as well as line current increase.
D. Both back emf as well as line current fall.
Answer» B. Back emf falls and line current increase.
Discussion
14.

What will happen if the back emf of a DC motor vanishes suddenly?

A. The motor will stop
B. The motor will continue to run
C. The armature may burn
D. The motor will run noisy
Answer» D. The motor will run noisy
Discussion
15.

What will happen if DC shunt motor is connected across AC supply?

A. Will run at normal speed
B. Will not run
C. Will Run at lower speed
D. Burn due to heat produced in the field winding
Answer» E.
Discussion