TRANSFORMER MCQ IMPORTANT FOR EXAM 20-20 | SET 01

A transformer is a passive electrical device that transfers electrical energy from one electrical circuit to one or more circuits. A varying current in any one coil of the transformer produces a varying magnetic flux, which, in turn, induces a varying electromotive force across any other coils wound around the same core. Electrical energy can be transferred between the (possibly many) coils, without a metallic connection between the two circuits. Faraday's law of induction discovered in 1831 described the induced voltage effect in any coil due to changing magnetic flux encircled by the coil.

MCQ of Transformer set 01

1.The main purpose of using core in transformer is to

a) Decrease reluctance of the common magnetic circuit
b) Decrease iron losses
c) Prevent hysteresis loses
d) Prevent eddy current losses

Ans: (a)

2. Transformer works on the principle of

a) Self induction
b) Mutual induction
c) Faraday’s law of electromagnetic induction
d) Self and mutual induction both

Ans: (d)

3. If dc voltage is applied to the primary of a transformer it may

a) Work
b) Burn the winding
c) Not work
d) Give lower voltage on the secondary side

Ans: (b)

4. Which of the following will improve the mutual coupling between primary and secondary of a transformer ?

a) Transformer oil of high breakdown voltage
b) Winding material of high resistivity
c) High reluctance magnetic core
d) Low reluctance magnetic core

Ans: (d)

5. Which type of core is used for a high-frequency transformer

a) Open iron core
b) Air core
c) Closed iron core
d) None of these

Ans: (b)

6. Transformer oil used in transformer provides

a) Insulation and cooling
b) Cooling and lubrication
c) Lubrication and insulation
d) Insulation, cooling and lubrication

Ans: (a)

7. Enamel layer is coated over the lamination of a transformer core to

a) Attain adhesion between the lamination
b) Prevent corrosion of laminations
c) Decrease the hum
d) Insulate the lamination from each other

Ans: (d)

8. The primary and secondary induced emfs E₁and E₂ in two-winding transformer are always

a) Antiphase with each other
b) In phase with each other
c) Equal in magnitude
d) Determined by load on transformer secondary

Ans: (b)

9. An step-up transformer increases

a) Current
b) Frequency
c) Voltage
d) Power

Ans: (c)

10. Eddy current losses in a transformer core may be reduced by

a) Reducing the air gap in the magnetic circuit

b) Reducing the thickness of lami-nations

c) Increasing the thickness of lami-nations

d) Increasing the gap in the magnetic circuit

Ans: (b)

11. In a transformer, the oil must be free from

a) sulphur
b) odour
c) moisture
d) both (a) and (c)

Ans: (d)

12. In a transformer, the magnetic coupling between the primary and secondary circuit can be increased by

a) increasing the number of turns
b) using soft material for winding
c) using magnetic core of low reluc-tance
d) using transformer oil better quality

Ans: (c)

13. If the density in the core of a transformer is increased

a) the frequency the secondary winding voltage increases
b) waveshape of the secondary winding voltage gets distorted
c) size of the transformer can be reduced
d) eddy current losses increase

Ans: (c)

14.The power factor in a transformer

a) is always unit
b) is always leading
c) is always lagging
d) depends on the power factor of load

Ans: (d)

15. Which of the following transformer will be largest is size?

a) 1 kVA, 50 Hz
b) 1 KVA, 60 Hz
c) 1KVA, 100Hz
d) 1KVA, 500 Hz

Ans: (d)

16. A transformer transforms

a) Current
b) Voltage
c) Frequency
d) Both voltage and current

Ans: (d)

17. A transformer does not change the following

a) Waveform
b) Frequency
c) Voltage
d) Both frequency and waveform

Ans: (d)

18. A transformer provides a path for magnetic flux of

a) High reluctance
b) High conductivity
c) Low reluctance
d) Low conductivity

Ans: (c)

19. An ordinary transformer works on

a) A.C
b) D.C
c) Both a.c. and d.c.
d) Pulsating d.c.

Ans: (a)

20. An ideal transformer is one which has

a) A common core for its primary and secondary winding

b) Core of stainless steel and winding of pure copper wire

c) No losses and magnetic leakage

d) Interleaved primary and secondary windings

Ans: (c)

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