Practical Electrical General Knowledge Questions - Set 05 - ObjectiveBooks

# G.K. Practice Test: Question Set - 05

1. The maximum temperature permitted for class A insulation is
(A) 180 °C
(B) 105 °C
(C) 120 °C
(D) 155 °C

2. The torque in the case of a wound rotor induction motor
(A) Increases as rotor resistance is increased
(B) Decreases as rotor resistance is increased
(C) Remains unaffected by increase/decrease of rotor resistance
(D) Is maximum when rotor is shorted

3. For hoist and cranes which motor should be selected
(A) 3 phase induction motor
(B) Synchronous motor
(C) D.C series motor
(D) D.C shunt motor

4. The power output of induction motor will be maximum when
(A) The equivalent load resistance is equal to the standstill reactance of the motor
(B) The equivalent load resistance is equal to the resistance of the motor
(C) The equivalent load resistance is equal to the standstill leakage impedance of the motor
(D) The slip is zero

5. The speed of induction motor is
(A) Synchronous speed
(B) Synchronous speed × slip
(C) Synchronous speed/(1- slip)
(D) Synchronous speed × (1- slip)

6. Which of the following motors has high starting torque?
(A) A.C motor
(B) Induction motor
(C) Synchronous motor
(D) D.C series motor

7. The starting torque of the slip ring induction motor is increased by
(A) Adding external resistance to the rotor
(B) Adding the external inductance to the rotor
(C) Adding both external resistance and inductance to the rotor
(D) Adding external capacitance to the rotor

8. An under-excited synchronous motor draws current at
(A) Unity power factor (p.f)
(C) Lagging p.f

9. The torque developed by an induction motor corresponding to zero slip is equal to
(A) Maximum
(B) Full rated capacity
(C) Zero
(D) Minimum

10. Which of the following motors is most frequently used in industries?
(A) Synchronous motor
(B) Commutator motor
(C) Single phase A.C motor
(D) 3 phase induction motor

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