A transformer is used to light a 100 W and 110 V lamp from

Home » Electricity and Magnetism » Alternating Current » Question

A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 amp, the efficiency of the transformer is approximately

1. 50%
2. 90%
3. 10%
4. 30%.

Correct Option: B

Efficiency of the transformer

η =	P_output	× 100 =	100	× 100 = 90.9%
	P_input		220 × 0.5