MULTIPLE CHOICE QUESTIONS
Q.1 In a 3-phase induction motor running at slip ‘s’ the mechanical power developed in terms of air gap power Pg is
(A) (s−1)Pg
.
(B) Pg/(1−s).
(C ) (1−s) .Pg
(D) s⋅Pg .
Q.2 In
a 3 – phase induction motor the maximum torque
(A)
is proportional to rotor resistance r2 .
(B)
does not depend on r2 .
(C)
is proportional to square root of r2
(D) is
proportional to square of r2.
Q.3 In
a d.c. machine, the armature mmf is
(A)
stationary w.r.t. armature.
(B) rotating w.r.t. field.
(C)
stationary w.r.t. field.
(D) rotating w.r.t. brushes.
Q.4 In
a transformer the voltage regulation will be zero when it operates at
(A)
unity p.f.
(B) leading p.f.
(C)
lagging p.f.
(D) zero p.f. leading.
Q.5 The maximum power in cylindrical and salient
pole machines is obtained respectively at load angles of
(A) 90o,
90o
(B) <90o
, 90o
(C) 90o
, >90o
(D) 90o , <90o
Q.6
The primary winding of a 220/6 V, 50 Hz transformer is energised from
110 V, 60 Hz supply. The secondary
output voltage will be
(A)
3.6 V.
(B) 2.5 V.
(C)
3.0 V.
(D) 6.0 V.
Q.7
The emf induced in the primary of a transformer
(A) is
in phase with the flux.
(B) lags behind the flux by 90 degree.
(C)
leads the flux by 90 degree.
(D) is in phase opposition to
that of flux.
Q.8
The relative speed between the
magnetic fields of stator and rotor under steady state operation is zero for a
(A) dc
machine.
(B) 3 phase induction machine.
(C) synchronous machine.
(D)
single phase induction machine.
Q.9
The current from the stator of an alternator is taken out to the
external load circuit through
(A)
slip rings.
(B) commutator segments.
(C)
solid connections.
(D) carbon brushes.
Q.10 A
motor which can conveniently be operated at lagging as well as leading power
factors is the
(A)
squirrel cage induction motor.
(B) wound rotor induction motor.
(C) synchronous
motor.
(D) DC shunt motor.
