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MCQ of Transformer page-25


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141. A transformer has primary to secondary turn ratio of 10. Every single ohm of reactance on secondary winding when referred to primary will be the same as

A) 0.1 ohm
B) 1 ohm
C) 10 ohm
D) 100 ohm.

Ans : (D)

142. Voltage transformer of which class of accuracy can be used for precision testing n standard laboratories ?

A) 1.00 class
B) 10 class
C) 5.00 class
D) 1000 class.

Ans : (A)

143. The core flux of a practical transformer with a resistive load

A) is strictly constant with load changes
B) increases linearly with load
C) increases as the square root of the load
D) decreases with increased load.

Ans : (A)

144. Over currents in a transformer affect

A) insulation life
B) temperature rise
C) mechanical stress
D) all of the above.

Ans : (D)

145. A tap changer is used on a transformer for

A) adjustments in primary voltage
B) adjustments in secondary voltage
C) adjustments in both primary and secondary voltages
D) adjustments in power factor.

Ans : (C)

146. An auto transformer used with a sodium vapour lamp should have high

A) leakage reactance of windings
B) VA rating
C) transformation ratio
D) winding resistance.

Ans : (A)

147. The most suitable material for transformer core is

A) Hot rolled grain oriented steel
B) Cold rolled grain oriented steel
C) Cast steel
D) Aluminium.

Ans : (B)

148. The efficiency of power transformer is around …………

A) 50%
B) 60%
C) 80%
D) 95%.

Ans : (D)

149. In performing short circuit test on transformer low voltage side is usually short circuited. This is because it has

A) More number of turns
B) Low terminal voltage and higher current rating
C) Easy access
D) Low insulation.

Ans : (B)

150. The magnetic materials that are used to prepare permanent magnets should have

A) small hysteresis loop
B) high retentivity
C) low coercive force
D) steepy rising magnetization curve.

Ans : (B)


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