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Basic Electrical MCQs – General Science MCQs – 4

If A.C is fed by mistake to a D.C motor, then the D.C motor will
(A) Burn as the eddy currents in the field produce heat
(B) Run at its normal speed
(C) Run at a lower speed
(D) Run continuously, but the sparking takes place at the brushes
Answer: Option A

The following motor is preferred for locomotives motor drives
(A) A.C Series motor
(B) Induction motor
(C) D.C Series motor
(D) Synchronous motor
Answer: Option C

Which of the following motors has high starting torque?
(A) D.C shunt motor
(B) Squirrel cage induction motor
(C) D.C Series motor
(D) A.C Series motor
Answer: Option C

In a D.C generator, following loss will be minimum
(A) Copper loss
(B) Iron loss
(C) Friction loss
(D) Shunt field copper loss
Answer: Option B

If the excitation to the field of the D.C motor is constant, then the torque developed in the motor is proportional to
(A) Armature current
(B) Field current
(C) Speed
(D) Magnetic flux
Answer: Option A

The torque of a D.C series motor with increase in speed
(A) Increases gradually
(B) Decreases linearly
(C) Remain constant
(D) First decreases rapidly and then slowly
Answer: Option D

The function of the commutator in a D.C machine is
(A) To change alternating current to a direct current
(B) To improve commutation
(C) To improve efficiency of motor
(D) To change alternating voltage to direct voltage
Answer: Option D

The torque in induction motor is proportional to
(A) Slip s
(B) 1/s
(C) s²
(D) 1 – s
Answer: Option A

Which of the following motors is usually used in household refrigerator?
(A) D.C shunt motor
(B) Reluctance motor
(C) Single phase induction motor (split phase start or induction run motor)
(D) Synchronous motor
Answer: Option C

The maximum temperature permitted for class A insulation is
(A) 180 °C
(B) 105 °C
(C) 120 °C
(D) 155 °C
Answer: Option B