MULTIPLE CHOICE QUESTIONS
Q.1 The maximum power for a given excitation in a synchronous motor is developed when the power angle is equal to
(A)
0o
(B) 45o
(C) 60o
(D) 90o
Q. 2 A commutator in a d.c. machine
(A)
Reduces power loss in armature.
(B)
Reduces power loss in field circuit.
(C)
Converts the induced a.c armature voltage into direct voltage.
(D)
Is not necessary.
Q.3 The speed of a d.c. shunt motor at no-load
is
(A)
5 to 10%
(B) 15 to 20%
(C)
25 to 30%
(D) 35 to 40%
Q.4 The efficiency of a transformer is mainly
dependent on
(A)
core losses.
(B) copper losses.
(C)
stray losses.
(D) dielectric
losses.
Q.5 When two transformers are operating in
parallel, they will share the load as under:
(A)
proportional to their impedances.
(B)
inversely proportional to their impedances.
(C)
50% - 50%
(D)
25%-75%
Q.6 If the voltage is reduced to half, the torque
developed by an induction motor will be reduced to
(A)
¼ of original torque.
(B) ½ of original torque.
(C) 1/8 of original torque.
(D) 1/16
of original torque.
Q.7 A
3-phase, 400 votts,
50 Hz, 100
KW, 4 pole squirrel cage
induction motor with a
rated slip
of 2% will have a rotor speed of
(A)
1500 rpm
(B) 1470 rpm
(C)
1530 rpm
(D) 1570 rpm
Q.8 If
the phase angle
of the voltage
coil of a
directional relay is 50o , the
maximum torque angle of the relay is
(A) 130o
(B) 100o
(C) 50o
(D) 25o
Q.9 A
220/440 V, 50
Hz, 5 KVA,
single phase transformer
operates on 220V,
40Hz supply with secondary winding open circuited. Then
(A) Both eddy current and hysteresis losses
decreases.
(B)
Both eddy current and hysteresis losses increases.
(C) Eddy
current loss remains the same but hysteresis loss increases.
(D) Eddy current loss increases but hysteresis
loss remains the same.
Q.10 A synchronous motor is operating on no-load
at unity power factor. If the field current is increased, power factor will
become
(A) Leading & current will decrease
(B) Lagging & current will increase.
(C) Lagging & current will decrease.
(D) Leading & current will increase.
