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

Options

A. 0.3
B. 0.5
C. 0.9
D. 0.1

Answer

C

Explanation

`eta = (P_("out"))/(P_("in")) = 100/(220 xx 0.5) = 0.9 = 90%`.