MULTIPLE CHOICE QUESTIONS
Q.1 Of the following statements concerning parallel operation
of transformers, the one which is not correct is
(A) transformers must have equal voltage ratings
(B) transformers must have same ratio of
transformation
(C) transformers must be operated at the same
frequency
(D) transformers must have equal kVA ratings.
Q.2 Statement: An auto-transformer is more efficient in transferring
energy from primary to secondary circuit.
Reason: Because it does so both inductively and conductively.
Key
(A) statement is false, reason is correct and relevant
(B) statement is correct, reason is correct but
irrelevant
(C) both statement and reason are correct and are
connected to each other as cause and effect
(D) both statement and reason are false.
Q.3 Out of the following given choices for poly phase
transformer connections which one will you select for three-to-two phase
conversion ?
(A) Scott
(B) star/star
(C) double Scott
(D) star/double-delta
Q.4 A T − T transformer cannot be paralleled with
......... transformer.
(A) V − V
(B) Y − Δ
(C) Y − Y
(D) Δ − Δ
Q.5 Instrument transformers are used on a.c. circuits
for extending the range of
(A) ammeters
(B) voltmeters
(C) wattmeters
(D) all of the above.
Q.6 Before removing the ammeter from a current
transformer, its secondary must be short-circuited in order to avoid
(A) excessive heating of the core
(B) high secondary e.m.f.
(C) increase in iron losses
(D) all of the above.
Q.7 A 220 V shunt motor develops a torque of 54 N-m at
armature current of 10 A. The torque produced when the armature current is 20
A, is
(A) 54 N-m
(B) 81 N-m
(C) 108 N-m
(D) None of the above
Q.8 The d.c. series motor should never be switched on
at no load because
(A) the field current is zero
(B) The machine does not pick up
(C) The speed becomes dangerously high
(D) It will take too long to accelerate.
Q.9 A shunt d.c. motor works on a.c. mains
(A) unsatisfactorily
(B) satisfactorily
(C) not at all
(D) none of the above
Q.10 A 200 V, 10 A motor could be rewound for 100 V, 20
A by using .......... as many turns per coil of wire, having .......... the
cross-sectional area.
(A) twice, half
(B) thrice, one third
(C) half, twice
(D) four times, one-fourth
