1- The no-load current drawn by transformer is usually, the per cent of the full-load current is a) 0.2 to 5 per cent b) 2 to 5 per cent c) 12 to 15 5 per cent d) 20 to 30 per cent c) 0.5, d) 0.35 2- The power factor of a transformer on no load will be about a) unity, b) 0.75, 3- The efficiency of a transformer will be maximum when a) copper losses = hysteresis losses c) copper losses = iron losses b) eddy current losses = copper losses d) hysteresis losses = eddy current losses 4-During the short circuit test, the core losses are negligible. This is because a) The voltage applied across the high voltage side is a fraction of its rated voltage b) The current on the low voltage side is very small. c) The power factor is high d) iron becomes fully saturated 5-While conducting short-circuit test on a transformer, the following side is short circuited a) Secondary side, b) Low voltage side c) High voltage side d) Primary side

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Electric machines/ I need to choose the correct answer with a brief explanation for it.
1- The no-load current drawn by transformer is usually, the per cent of the full-load current is
a) 0.2 to 5 per cent
b) 2 to 5 per cent
c) 12 to 15 per cent d) 20 to 30 per cent
2- The power factor of a transformer on no load will be about
a) unity,
b) 0.75,
c) 0.5,
3- The efficiency of a transformer will be maximum when
a) copper losses hysteresis losses
c) copper losses = iron losses
d) 0.35
b) eddy current losses = copper losses
d) hysteresis losses = eddy current losses
4-During the short circuit test, the core losses are negligible. This is because
a) The voltage applied across the high voltage side is a fraction of its rated voltage
b) The current on the low voltage side is very small.
c) The power factor is high
d) iron becomes fully saturated
5-While conducting short-circuit test on a transformer, the following side is short circuited
a) Secondary side, b) Low voltage side
6- The core loss of a transformer depends upon :
a) the frequency and the maximum flux density
c) rated current
c) High voltage side
d) Primary side
b) Induced Voltage
d) rated voltage
7- The no load current in a transformer lags behind the applied voltage by an angle of about
a) 120 degree
b) 75 degree c) 45 degree
d)180 degree
8- The hysteresis loss in a transformer is 500 watts at 50 Hz. Its loss at 80 Hz will be
a) 312.5 watts
b) 500 watts
c) 200 watts
9- Power transformers are designed to have maximum efficiency at
d) 800 watts
a) nearly full load b) 70% full load
c) 50% full load
d) no load
10- A transformer operates maximum efficiently at 3/4th full load. Its iron (Pi) and copper loss (Pcu)
are related as:
a) Pi 1.778 Pcu
b) Pi 1.333 Pcu
c) Pi=0.75 Pcu
d) Pi=0.5625 Pcu
Transcribed Image Text:1- The no-load current drawn by transformer is usually, the per cent of the full-load current is a) 0.2 to 5 per cent b) 2 to 5 per cent c) 12 to 15 per cent d) 20 to 30 per cent 2- The power factor of a transformer on no load will be about a) unity, b) 0.75, c) 0.5, 3- The efficiency of a transformer will be maximum when a) copper losses hysteresis losses c) copper losses = iron losses d) 0.35 b) eddy current losses = copper losses d) hysteresis losses = eddy current losses 4-During the short circuit test, the core losses are negligible. This is because a) The voltage applied across the high voltage side is a fraction of its rated voltage b) The current on the low voltage side is very small. c) The power factor is high d) iron becomes fully saturated 5-While conducting short-circuit test on a transformer, the following side is short circuited a) Secondary side, b) Low voltage side 6- The core loss of a transformer depends upon : a) the frequency and the maximum flux density c) rated current c) High voltage side d) Primary side b) Induced Voltage d) rated voltage 7- The no load current in a transformer lags behind the applied voltage by an angle of about a) 120 degree b) 75 degree c) 45 degree d)180 degree 8- The hysteresis loss in a transformer is 500 watts at 50 Hz. Its loss at 80 Hz will be a) 312.5 watts b) 500 watts c) 200 watts 9- Power transformers are designed to have maximum efficiency at d) 800 watts a) nearly full load b) 70% full load c) 50% full load d) no load 10- A transformer operates maximum efficiently at 3/4th full load. Its iron (Pi) and copper loss (Pcu) are related as: a) Pi 1.778 Pcu b) Pi 1.333 Pcu c) Pi=0.75 Pcu d) Pi=0.5625 Pcu
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