DC Motors MCQs
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The efficiency of any electrical machine/apparatus will be high, if
- A. its losses are minimum
- B. its losses are more
- C. voltage applied is constant
- D. the current drawn is minimum
- Correct Answer: Option A
A starter is necessary to start a dc motor because
- A. it starts the motor
- B. it limits the speed of the motor
- C. it limits the back emf to a safe value
- D. it limits the starting current to a safe value
- Correct Answer: Option D
The power stated on the name plate of any motor is always
- A. the output power at the shaft
- B. the power drawn in kVA
- C. the power drawn in kW
- D. the gross power
- Correct Answer: Option A
The output power of any electrical motor is taken from
- A. the armature
- B. the coupling mounted on the shaft
- C. the conductors
- D. the poles
- Correct Answer: Option B
The armature current drawn by any dc motor is proportional to
- A. the voltage applied to the motor
- B. the torque required
- C. the flux required in the motor
- D. the speed of the motor
- Correct Answer: Option B
The torque of a motor is
- A. the force in N-m acting on the rotor
- B. the product of tangential force on the rotor and its radius
- C. the electrical power in kW
- D. the power given to load being driven by the motor
- Correct Answer: Option B
Armature torque of a dc motor is given by
- A. T = 0.159ΦZIa(P/a) kg-m
- B. T = 0.1620/2Ia(P/a) N-m
- C. T = 0.159Eb/N Ia N-m
- D. T = P/a kg-m
- Correct Answer: Option C
One dc motor drives another dc motor. The second dc motor when excited and driven
- A. runs
- B. does not run as a generator
- C. runs as a generator
- D. also runs as a motor
- Correct Answer: Option C
In dc shunt motor, if the terminal voltage is reduced to half and torque remains the same, then
- A. speed will be half and armature current also will be half
- B. speed will be half and armature current remains the same
- C. speed will be half and armature current becomes double
- D. speed and armature current will remain the same
- Correct Answer: Option C
The shunt current flowing in short shunt compound-wound motor is given by
- A. Ish = V/Rsh
- B. Ish = (V IsRs)/Rsh
- C. Ish = V - IsRs/Rsh
- D. none of these
- Correct Answer: Option B