EEE MCQ : Transformer - E Tips BD

## Sunday, August 9, 2015

A transformer is a static electrical device that transfer electrical energy without changing its frequency by inductive coupling between its winding circuits. A varying current in the primary winding creates a varying magnetic flux in the transformer’s core and thus a varying magnetic flux through the secondary winding. This varying magnetic flux induces a varying electromotive force (emf) or voltage in the secondary winding.

Answer লেখা ইমেজে ক্লিক করলে উত্তর অপশন দেখাবে।
1) 1. What is the condition for maximum efficiency of a transformer-
A) when copper loss = core loss
B) when copper loss = hysteresis loss
C) When transformer run by unity power factor
D) when copper loss = eddy current loss

2) The leakage flux in a transformer depends upon
A) the frequency
C) the mutual flux.
D) the applied voltage.

3) Oil is provided in an oil filled transformer for
A) insulation
B) lubrication
C) cooling
D) both cooling and insulation.

4) What kVA rating is required for a transformer that must handle a maximum load current of 8 A with a secondary voltage of 2 kV?
A) 132kV
B) 33kV
C) 66kV
D) 16kV.

5) Transformer is used for—
A) to step down voltage
B) to step up and step down primary voltage
C) to step up voltage
D) None of above.

6) Which of the following is minimized by laminating the core of a transformer?
A) Eddy current loss.
B) Copper loss
C) Stray loss
D) Hysteresis loss

7) When a 400Hz transformer is operated at 50 Hz, its KVA ratings is–
A) unaffected
B) reduced
C) increased by 8 times
D) none of above

8) The main purpose of performing open circuit test in a transformer is to measure its–
A) vector group
B) insulation resistance
C) copper loss
D) core loss

9) Does the transformer draw any current when secondary is open?
A) Yes
B) No

10) The copper loss of a transformer at full load is 40W. What would be at half load-
A) 10W
B) 20W
C) 40W
D) 80W

11) Lamination of transformer core is made of
A) cast iron
B) aluminium
C) copper
D) silicon steel.

12) When a 6 V battery is connected across the primary of a transformer with a turns ratio of 8, the secondary voltage is
A) 0V
B) 12V
C) 24V
D) 48V

13) When the turns ratio of a transformer is 20 and the primary ac voltage is 12 V, the secondary voltage is
A) 24V
B) 120V
C) 240V
D) 440V

14) Breather is provided in a transformer to
A) absorb moisture of air during breathing.
B) filter of transformer oil
C) provide cold air in transformer
D) none of above

15) The basic function of transformer is to change?
A) the level frequency
B) the level voltage
C) power level
D) power factor level

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