MULTIPLE CHOICE QUESTIONS
Q.1 In a two-winding transformer, the e.m.f. per turn in secondary winding is always.......the induced e.m.f. power turn in primary.
(A) equal to K times
(B) equal to 1/K times
(C) equal to
(D) greater than.
Q.2 In relation to a transformer, the ratio 20 : 1
indicates that
(A) there are 20 turns on primary one turn on
secondary
(B) secondary voltage is 1/20th of primary voltage
(C) primary current is 20 times greater than the
secondary current.
(D) for every 20 turns on primary, there is one turn
on secondary.
Q.3 In performing the short circuit test of a
transformer
(A) high voltage side is usually short circuited
(B) low voltage side is usually short circuited
(C) any side is short circuited with preference
(D) none of the above.
Q.4 The equivalent resistance of the primary of a
transformer having K = 5 and R1 = 0.1 ohm
when referred to secondary becomes.......ohm.
(A) 0.5
(B) 0.02
(C) 0.004
(D) 2.5
Q.5 A transformer has negative voltage regulation when
its load power factor is
(A) zero
(B) unity
(C) leading
(D) lagging.
Q.6 The primary reason why open-circuit test is
performed on the low-voltage winding of the
transformer is that it
(A) draws sufficiently large on-load current for
convenient reading
(B) requires least voltage to perform the test
(C) needs minimum power input
(D) involves less core loss.
Q.7 No-load test on a transformer is carried out to
determine
(A) copper loss
(B) magnetising current
(C) magnetising current and no-load loss
(D) efficiency of the transformer.
Q.8 The main purpose of performing open-circuit test
on a transformer is to measure its
(A) Cu loss
(B) core loss
(C) total loss
(D) insulation resistance.
Q.9 During short-circuit test, the iron loss of a
transformer is negligible because
(A) the entire input is just sufficient to meet Cu
losses only
(B) flux produced is a small fraction of the normal
flux
(C) iron core becomes fully saturated
(D) supply frequency is held constant.
Q.10 The iron loss of a transformer at 400 Hz is 10 W.
Assuming that eddy current and hysteresis losses vary as the square of flux
density, the iron loss of the transformer at rated voltage but at 50 Hz would
be....... watt.
(A) 80
(B) 640
(C) 1.25
(D) 100