Hi friends, this post is about transformer objectives. These are some of the questions asked in previous question papers of Gate, IES and other competitive exams. check out and comment if you have any doubts.....
1) The core flux in transformer depends mainly on
A) supply voltage
B) supply voltage and frequency
C) supply voltage, frequency and load
D) supply voltage and load but independent of frequency
Ans:B
2) The primary and secondary winding of a power transformer always have
A) a common magnetic circuit
B) separate magnetic circuit
C) wire of same size
D) same number of turns
Ans:A
3) On no-load phasor diagram of transformer, the core loss component of the current remains in phase with
A) no-load current
B) primary supply voltage
C) core flux
D) primary induced voltage
Ans:B
4) The power factor of a power transformer on no-load will be about
A) unity
B) 0.75
C) 0.5
D) 0.35
Ans:D
5) For an ideal transformer the winding should have
A) maximum resistance on primary side and least resistance on secondary side
B) least resistance on primary side and maximum resistance on secondary side
C) equal resistance on primary and secondary sides
D) no ohmic resistance on either side
Ans:D
6) The core flux of a practical transformer with a resistance 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 increase of load
Ans:A
7) The power factor of a transformer on no-load is poor due to
A) magnetizing reactance of the transformer
B) open-circuited secondary
C) low primary winding resistance
D) low no-load current
Ans:A
8) If the supply frequency of a transformer is increased, keeping the supply voltage constant, then
A) both magnetising component and core loss component of current will decrease
B) both magnetising component and core loss component of current will increase
C) magnetising component of current will increase while core loss component of current will decrease
D) magnetising component of current will decrease while core loss component of current will increase
Ans:A
9) In a transformer, the excited current will be in phase quadrature with the impressed voltage provided
A) only the leakage impedance drop is ignored
B) only the core loss is ignored
C) both the leakage impedance drop and the core loss are ignored
D) only the no-load copper loss is ignored
Ans:C
10) If the applied voltage to a transformer primary is increased by keeping the V/F ratio fixed, then the magnetizing current and the core loss will, respectively
A) decrease and remain the same
B) increase and decrease
C) both remain the same
D) remain the same and increase
Ans:D
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