D.C. Motors MCQs

1.What principle does regenerative braking rely on?

The back electromotive force is lower than the input voltageThe back electromotive force equals the input voltageThe rotor's back electromotive force exceeds the input voltageNone of these options

2.The Ward Leonard technique for regulating motor speed primarily involves which method?

Controlling the field windingAdjusting the armature voltageUsing a field diverterVarying the supply frequency

3.Which test is suitable for conducting on a DC series motor?

4.What effect does armature reaction have on the speed of a DC motor?

5.In a DC motor, how is the interpole winding typically connected?

In series with the main field windingIn series with the armature windingConnected in parallel with the main field windingConnected in parallel with the armature windingNone of the above

6.Why is it unsafe to start a DC series motor when it is running without any load?

It will be unable to generate initial torqueIt cannot begin operation without a load attachedIt may accelerate to an excessively high speed, causing damageIt will consume excessive current but produce inadequate torqueIt will immediately overheat and fail

7.Which technique is commonly employed to regulate the speed of a DC shunt motor?

Adjusting the supply voltageModifying the magnetic fluxUsing a variable resistor in the circuitAll the methods mentioned above

8.What will happen to the speed of a DC shunt motor if the resistance in its field winding is raised?

9.How does the speed of a DC series motor change as the temperature rises?

10.How does the speed of a DC shunt motor change as the temperature rises?

11.In which device do the induced emf and the armature current flow in opposite directions?

Direct current generatorDirect current motorElectrical transformerAll of these devices

12.When the load on a DC shunt motor rises, what causes its speed to drop slightly?

13.When one DC motor powers another DC motor, how does the second motor behave when it is energized and driven?

It operates as a generatorIt does not function as a generatorIt continues to run as a motor but eventually stops

14.How can the speed of a D.C. shunt motor be increased beyond its full load speed?

15.Where do the iron losses primarily take place in a DC motor?

Within the field windingInside the armature coreAt the brush contactsOn the commutator surface

16.Which type of D.C. motor exhibits the greatest self-relieving characteristic?

Series motorShunt motorCumulatively compounded motorDifferentially compounded motor

17.Which type of motor is best suited for driving a load that remains nearly zero for a portion of the cycle and reaches a peak value briefly?

18.Which type of motor is best suited to drive a load that requires a consistent minimum torque most of the time, but occasionally demands a higher peak torque for short periods?

Series motorShunt motorCompound motorAny of the above

19.What will happen if the shunt field circuit of a DC shunt motor operating under full load suddenly opens?

The armature will draw a large current, which may cause it to burn out.The motor speed will increase excessively, potentially damaging the armature due to high centrifugal forces.The motor will continue to run without any change.The motor will immediately stop functioning.The motor will reverse its direction.

20.Which type of controller is suitable for a D.C. motor rated 12 H.P. or higher when frequent starting, stopping, reversing, and speed regulation are needed?

A drum type controller is employedA three-point starter is utilizedA four-point starter is appliedAny of the above methods can be used