300 Important DC Motor MCQ Questions & Answers with Explanation | PDF Free Download
1.Which of the following dc motors has least drop in speed from no load to rated full load?
- ASeries motors with interpoles
- BSeries motors without interpoles
- CShunt motors with interpoles
- DCumulative compound motors with interpoles
2.A dc motor is to drive a load which is almost nil for certain part of the load cycle and peak value for short duration. The most suitable dc motor is
- ASeries
- BShunt
- CDifferential compound
- DCumulative compound
3.On switching a dc motor to dc supply mains, it is found to rotate in the direction opposite to that for which it is designed. The dc motor is
- ADifferential compound
- BCumulative compound
- CSeries
- DShunt
4.For the same power output rating and full-load speed, the motor that will have poorest starting torque is
- ACumulative compound
- BDifferential compound
- CSeries
- DShunt
5.A motor used for punching machine is usually subjected to
- AFull load continuously
- BPart of full load continuously
- CNo load
- DIntermittent load
6.The most suitable dc motor for continuously running rolling mills with intermittent loading is
- ADc series motor
- BDc shunt motor
- CDc differentially compounded motor
- DDc cumulatively compounded motor
7.The speed of a dc motor depends upon
- AFlux per pole
- BApplied voltage to armature
- CVoltage drop in armature circuit resistance
- DAll of the above
8.The field flux method of speed control of dc shunt motor is generally used for
- AConstant hp drive below the base speed
- BConstant torque drive above the abase speed
- CConstant torque drive below the base speed
- DConstant hp drive above the base speed
9.The resistance of the field regulator of a dc shunt motor is of the order of
- A100
- B10
- C2
- D0.5
10.The speed of a dc shunt motor can be raised above its rated value by
- AInserting an additional resistance in the armature circuit
- BInserting an additional resistance in the field circuit
- CReducing the applied voltage
- DUsing either of the above methods
11.Which of the following statements associated with field control of dc shunt motors is correct?
- ASpeed can be varied below and above the rated speed to any extent
- BSpeed can be varied above to any extent and below to a certain extent
- CSpeed can be varied above to the extent of satisfactory commutation and below no variation
- DSpeed can be varied above to the extent of satisfactory commutation and below to any extent
12.A dc shunt motor is supplying a load at its rated speed. The speed can be reduced by
- AArmature circuit resistance control
- BField resistance control
- CWard Leonard control
- DAny of the above
13.The speed of a dc shunt motor supplying a load at its rated speed can be reduced by
- AConnecting an additional resistance in the armature circuit
- BConnecting an additional resistance in the field circuit
- CIncreasing the applied voltage
- DAny of the above methods
14.A Dc shunt motor is operating at no load. If the armature is shunted by a resistance, it's speed will
- AIncrease
- BDecrease
- CRemain the same
- DBe unpredictable
15.The shunted armature speed control method for dc shunt motor is
- ALess expensive
- BLess wasteful
- CSuitable for rapidly changing loads
- DNone of the above
16.The armature voltage control is considered suitable for a dc motor driven at constant
- ATorque
- BSpeed
- CPower
- DCurrent
17.A 220V, DC shunt motor is operating at a speed of 1,440 rpm. The armature resistance is 1.0 ohm and armature current is 10A If the excitation of the machine is reduced by 10%, the extra resistance to be put in the armature circuit to maintain the same speed and torque will be
- A1.79 ohm
- B2.1 ohm
- C3.1 ohm
- D18.9 ohm
18.For the motor to deliver a torque of 2.5 Nm at 1400 rpm the armature voltage to be applied is
- A125.5V
- B193.3V
- C200V
- D241.7V
19.For a constant supply voltage, what are the effects of inserting a series resistance in the filed circuit of a dc shunt motor, on its speed and torque?
- ASpeed will decrease and the torque will decrease
- BSpeed will increase and the torque will increase
- CSpeed will increase and the torque will decrease
- DSpeed will decrease and the torque will increase
20.In a Ward Leonard drive, if the filed current of the dc generator is suddenly reduced, the controlled dc motor operates
- AStill in the motoring mode
- BIn dynamic braking mode
- CIn counter current braking mode
- DIn regenerative braking mode