MULTIPLE CHOICE QUESTIONS
Q.1 The all-day efficiency of a transformer depends
primarily on
(A) its copper loss
(B) the amount of load
(C) the duration of load
(D) both (b) and (c).
Q.2 The marked increase in kVA capacity produced by
connecting a 2 winding transformer as an autotransfomer is due to
(A) increase in turn ratio
(B) increase in secondary voltage
(C) increase in transformer efficiency
(D) establishment of conductive link between primary
and secondary.
Q.3 The kVA rating of an ordinary 2-winding
transformer is increased when connected as an
autotransformer because
(A) transformation ratio is increased
(B) secondary voltage is increased
(C) energy is transferred both inductively and conductivity
(D) secondary current is increased.
Q.4 The saving in Cu achieved by converting a
2-winding transformer into an autotransformer
is determined by
(A) voltage transformation ratio
(B) load on the secondary
(C) magnetic quality of core material
(D) size of the transformer core.
Q.5 An autotransformer having a transformation ratio
of 0.8 supplies a load of 3 kW. The power transferred conductively from primary
to secondary is.......kW.
(A) 0.6
(B) 2.4
(C) 1.5
(D) 0.27
Q.6 The essential condition for parallel operation of
two 1-φ transformers is that they should have the same
(A) polarity
(B) kVA rating
(C) voltage ratio
(D) percentage impedance.
Q.7 If the impedance triangles of two transformers
operating in parallel are not identical in shape and size, the two transformers
will
(A) share the load unequally
(B) get heated unequally
(C) have a circulatory secondary current even when
unloaded
(D) run with different power factors.
Q.8 Two transformers A and B having equal outputs and
voltage ratios but unequal percentage impedances of 4 and 2 are operating in
parallel. Transformer A will be running over-load by ....... percent.
(A) 50
(B) 66
(C) 33
(D) 25
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
