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Electrician
Electrician Set-1
DC Motors
27

DC Motors MCQ - Electrician (Set-1) with Answers

27) You notice that a d.c. motor starts with jerk when starting the motor. What may be the fault for this effect ?

Line voltage too high

Short-circuit in the field winding

Pitted starter contact terminals

Wrong grade of carbon brushes

Answer is:

Pitted starter contact terminals

DC Motors MCQ - Electrician (Set-1) with Answers

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Related DC Motors MCQ - Electrician (Set-1) with Answers

28) The speed of a d.c. shunt motor of 3 kW is 2000 r.p.m. when connected to a constant voltage supply. The speed is to be varied upto 2500 r.p.m. What speed control method is to be used ?

Increasing the back e.m.f. with a resistor

Limiting the armature current with a shunt resistor

Changing the voltage with a starter

Changing the field current by a field rheostat

Answer is:

Changing the field current by a field rheostat

29) If the current in the armature of a d.c. series motor is reduced by 50%, the torque of the motor will become :

50%

25%

150%

200%

Answer is:

25%

30) If the load and flux of a D.C. motor are held constant, and the voltage applied across its armature is increased by 5 percent, the speed of the motor will :

increase by 5 percent

decrease by 5 percent

not change

infinity

Answer is:

increase by 5 percent

31) You have to change the defective motor of an electric locomotive. Which type of motor would you choose ?

DC differential compound motor

DC shunt motor

DC series motor

Separately excited motor

Answer is:

DC series motor

DC Motors MCQ - Electrician (Set-1) with Answers

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