MULTIPLE CHOICE QUESTIONS
Q.1 A hysteresis motor
(A) is not a self-starting motor.
(B) is a constant speed motor.
(C) needs dc excitation.
(D) can not be run in reverse speed.
Q.2 The most suitable servomotor for low power applications is
(A) a dc series motor.
(B) a dc shunt motor.
(C) an ac two-phase induction motor.
(D) an ac series motor.
Q.3 A two-winding single phase transformer has a voltage regulation of 4.5% at full-load and unity power-factor. At full-load and 0.80 power-factor lagging load the voltage regulation will be
(A) 4.5%.
(B) less than 4.5%.
(C) more than 4.5%.
(D) 4.5% or more than 4.5%.
Q.4 In a dc shunt motor the terminal voltage is halved while the torque is kept constant. The resulting approximate variation in speed ‘ ω’ and armature current ' ‘Ia’ will be
(A) Both ω and Ia are doubled.
(B) ω is constant and Ia is doubled.
(C) ω is doubled while Ia is halved.
(D) ω is constant but Ia is halved.
Q.5 A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole, induction motor. When the motor is delivering rated output, the slip is found to be 0.05. The speed of the rotor m.m.f. relative to the rotor structure is
(A) 1500 r.p.m.
(B) 1425 r.p.m.
(C) 25 r.p.m.
(D) 75 r.p.m.
Q.6 An alternator is delivering rated current at rated voltage and 0.8 power-factor lagging case. If it is required to deliver rated current at rated voltage and 0.8 power-factor leading, the required excitation will be
(A) less.
(B) more.
(C) more or less.
(D) the same.
Q.7 A ceiling fan uses
(A) split-phase motor.
(B) capacitor start and capacitor run motor.
(C) universal motor.
(D) capacitor start motor.
Q.8 A stepper motor is
(A) a dc motor.
(B) a single-phase ac motor.
(C) a multi-phase motor.
(D) a two phase motor.
Q.9 The drive motor used in a mixer-grinder is a
(A) dc motor.
(B) induction motor.
(C) synchronous motor.
(D) universal motor.
Q.10 A 1:5 step-up transformer has 120V across the primary and 600 ohms resistance across the secondary. Assuming 100% efficiency, the primary current equals
(A) 0.2 Amp.
(B) 5 Amps.
(C) 10 Amps.
(D) 20 Amps.
