# DC Motor MCQs: DC Motors in Electrical Engineering

DC Motor MCQs. Questions and Answers in Multiple Choice form on the topic of DC Motors.

## DC Motor MCQs

The speed of a D.C. shunt motor more than its full-load speed can be obtained by ?

A. decreasing the field current
B. increasing the field current
C. decreasing the armature current
D. increasing the armature current

A. decreasing the field current

The starting resistance of a D.C. motor is generally ?

A. low
B. around 500 Q
C. 1000 Q
D. infinitely large

A. low

The speed of a D.C. series motor is ?

A. proportional to the armature current
B. proportional to the square of the armature current
C. proportional to field current
D. inversely proportional to the armature current

D. inversely proportional to the armature current

The power mentioned on the name plate of an electric motor indicates ?

A. the power drawn in kW
B. the power drawn in kVA
C. the gross power
D. the output power available at the shaft

D. the output power available at the shaft

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

A. Series motor
B. Shunt motor
C. Cumulatively compounded motor
D. Differentially compounded motor

A. Series motor

Three point starter can be used for ?

A. series motor only
B. shunt motor only
C. compound motor only
D. both shunt and compound motor

D. both shunt and compound motor

DC Motor MCQs

The speed of a D.C. shunt motor can be increased by ?

A. increasing the resistance in armature circuit
B. increasing the resistance in field circuit
C. reducing the resistance in the field circuit
D. reducing the resistance in the armature circuit

B. increasing the resistance in field circuit

Ward-Leonard control is basically a ?

A. voltage control method
B. field divertor method
C. field control method
D. armature resistance control method

A. voltage control method

The current drawn by the armature of D.C. motor is directly proportional to ?

A. the torque required
B. the speed of the motor
C. the voltage across the terminals
D. none of the above

A. the torque required

If the field of dc shunt motor gets opened while motor is running ?

A. the speed of motor will be reduced %
B. the armature current will reduce
C. the motor will attain dangerously high speed 1
D. the motor will continue to nuvat constant speed

C. the motor will attain dangerously high speed 1

No-load speed of which of the following motor will be highest ?

A. Shunt motor
B. Series motor
C. Cumulative compound motor
D. Differentiate compound motor

B. Series motor

Starters are used with D.C. motors because ?

A. these motors have high starting torque
B. these motors are not self-starting
C. back e.m.f. of these motors is zero initially
D. to restrict armature current as there is no back e.m.f. while starting

D. to restrict armature current as there is no back e.m.f. while starting

DC Motor MCQs

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

A. interchanging supply terminals
B. interchanging field terminals
C. either of A. and B. above
D. None of the above

B. interchanging field terminals

Which of the following application requires high starting torque ?

A. Lathe machine
B. Centrifugal pump
C. Locomotive
D. Air blower

C. Locomotive

If a D.C. motor is connected across the A.C. supply it will ?

A. run at normal speed
B. not run
C. run at lower speed
D. burn due to heat produced in the field winding by eddy currents

D. burn due to heat produced in the field winding by eddy currents

Which D.C. motor is preferred for elevators ?

A. Shunt motor
B. Series motor
C. Differential compound motor
D. Cumulative compound motor

D. Cumulative compound motor

When two D.C. series motors are connected in parallel, the resultant speed is ?

A. more than the normal speed
B. loss than the normal speed
C. normal speed
D. zero

C. normal speed

In a D.C. shunt motor speed is ?

A. independent of armature current
B. directly proportional to the armature current
C. proportional to the square of the current
D. inversely proportional to the armature current

A. independent of armature current

DC Motor MCQs

What will happen if the back e.m.f. of a D.C. 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

C. The armature may burn

A three point starter is considered suitable for ?

A. shunt motors
B. shunt as well as compound motors
C. shunt, compound and series motors
D. all D.C. motors

B. shunt as well as compound motors

DC series motors are used ?

C. where constant operating speed is needed
D. in none of the above situations

D. in none of the above situations

The armature voltage control of D.C. motor provides ?

A. constant voltage drive
B. constant current drive
C. constant torque drive
D. none of the above

C. constant torque drive

The armature voltage control of D.C. motor provides ?

A. constant torque drive
B. constant voltage drive
C. constant current drive
D. none of the above

A. constant torque drive

Torque developed by a D.C. motor depends upon ?

A. magnetic field
B. active length of the conductor
C. current flow through the conductors
D. number of conductors
F. all above factors

F. all above factors

DC Motor MCQs

Which motor should not be started on no-load ?

A. Series motor
B. Shunt motor
C. Cumulatively compounded motor
D. Differentially compounded motor

A. Series motor

In a manual shunt motor starter ?

A. over load relay is connected in series and no volt relay in parallel with the load
B. over load relay is connected in parallel and no volt relay in series with the load
C. over load relay and no volt relay are both connected in series with the load
D. over load relay and no volt relay are both connected in parallel with the load

A. over load relay is connected in series and no volt relay in parallel with the load

For constant torque drive which speed control method is preferred ?

A. Field control
B. Armature voltage control
C. Shunt armature control

B. Armature voltage control

The condition for maximum efficiency for a D.C. generator is ?

A. eddy current losses = stray losses
B. hysteresis losses = eddy current losses
C. copper losses = 0
D. variable losses = constant losses

D. variable losses = constant losses

Hopkinson’s test on D.C. machines is conducted at ?

In the D.C. motor the iron losses occur in ?

A. the field
B. the armature
C. the brushes
D. the commutator

B. the armature

How interpoles are connected in a dc generator ?

A. series with field winding
B. series speed armature winding
C. parallel big field winding
D. parallel with armature winding