Question

A transformer is essentially an a.c. device. It cannot work on d.c. It changes alternating voltages or currents. It does not affect the frequency of a.c. It is based on the phenomenon of mutual induction. A transformer essentially consists of two coils of insulated copper wire having different numbers of turns and wound on the same soft iron core.

The number of turns in the primary and secondary coils of an ideal transformer is 2000 and 50 respectively. The primary coil is connected to a main supply of 120 V and secondary coil is connected to a bulb of resistance 0.6 Ω.

Power in primary coil is ______.

Options

• 20 W

• 5 W

• 10 W

• 15 W

Answer 1

Power in primary coil is 15 W.

Explanation:

Power in primary, P_p = E_p × I_p = 120 × 0.125 = 15 W