1. Which of the following property is not necessarily desirable in the material for transformer core ?

Mechanical strength

Low hysteresis loss

High thermal conductivity

High permeability

Answer: High thermal conductivity

Explanation:


2. The highest voltage for transmitting electrical power in India is ?

33 kV

66 kV

132 kV

400 kV

Answer: 400 kV

Explanation:


3. Material used for construction of transformer core is usually ?

wood

copper

aluminium

silicon steel

Answer: silicon steel

Explanation:


4. A transformer cannot raise or lower the voltage of a D.C. supply because ?

there is no need to change the D.C. voltage

a D.C. circuit. bas more losses

Faraday's laws of electromagnetic induction are not valid since the rate of change of flux is zero

none of the above

Answer: Faraday's laws of electromagnetic induction are not valid since the rate of change of flux is zero

Explanation:


5. In a transformer the energy is conveyed from primary to secondary ?

through cooling coil

through air

by the flux

none of the above

Answer: by the flux

Explanation:


6. A transformer can have zero voltage regulation at ?

leading power factor

lagging power factor

unity power factor

zero power factor

Answer: leading power factor

Explanation:


7. The core used in high frequency transformer is usually ?

copper core

cost iron core

air core

mild steel core

Answer: air core

Explanation:


8. Losses which occur in rotating electric machines and do not occur in transformers are ?

friction and windage losses

magnetic losses

hysteresis and eddy current losses

copper losses

Answer: friction and windage losses

Explanation:


9. The distribution transformers are designed to keep the iron-losses minimum because ?

the primary of distribution transformer is energised for all the twenty four hours

iron losses may damage the insulation

iron-losses will heat up the coil

none of the above

Answer: the primary of distribution transformer is energised for all the twenty four hours

Explanation:


10. The iron losses of a transformer can be calculated by knowing the weights of ?

copper winding only

yokes only

cores only

cores and yokes

Answer: cores and yokes

Explanation: