AC MACHINES 16

1. Which of the following does not change in an ordinary transformer?
a) voltage
b) current
c) frequency
d) phase angle
ans. c

2. The color of fresh dielectric oil for a transformer is
a) pale yellow
b) dark brown
c) while grey
d) colourless
ans. a

3. In a transformer if in place of sine wave, a peaked voltage is fed to the primary,
a) the iron losses will be less
b) the iron losses will be more
c) the copper losses will be less
d) the noise level will be low
ans. a

4. The path of the magnetic flux in a transformer should have
a) low reluctance
b) low resistance
c) high reluctance
d) high resistance
ans. a

5. The function of breather in a transformer is
a) to filter the transformer oil
b) to provide oxygen to the cooling oil
c) to provide cooling air
d) to arrest the flow of moisture when outside air enters the transformer
ans. d

6. Transformer works on
a) ac only
b) dc only
c) both ac and dc
d) pulsating dc
ans. c

7. Iron losses in a transformer occur in
a) core
b) winding
c) insulating
d) main body
ans. a

8. Transformers use laminated core
a) to reduce eddy current loss
b) to reduce eddy current and hysteresis loss
c) to reduce copper loss
d) none of these
ans. a

9. In a transformer with closed magnetic coupling between primary and secondary windings.
a) efficiency will he high
b) all day efficiency will be high
c) regulation will be good
d) none of these
ans. c

10. The number of turns in the primary winding of a transformer depends on
a) input voltage
b) input current
c) both input voltage and current
d) none of these
ans. a