Transformer is used to light 100 W and 110 V lamp using a 220 V main supply. If the supply current i

Question

Transformer is used to light 100 W and 110 V lamp using a 220 V main supply. If the supply current is 0.5 A , then the efficiency of the transformer is\

Professor PC Thomas Classes · Answer

Here, $\mathrm{P}_{0}=100 \mathrm{~W}, \mathrm{~V}_{\mathrm{S}}=110 \mathrm{~V}$ $$ \mathrm{V}_{\mathrm{P}}=220 \mathrm{~V}, \mathrm{I}_{\mathrm{P}}=0.5 \mathrm{~A} $$ Efficiency of\ transformer,\ $\eta=\frac{	ext { output power }}{	ext { input power }} 	imes 100$\ $	herefore \eta=\frac{\mathrm{P}_{0}}{\mathrm{P}_{\mathrm{i}}} 	imes 100=\frac{\mathrm{P}_{0}}{\mathrm{~V}_{\mathrm{P}} \mathrm{I}_{\mathrm{p}}} 	imes 100$\ $=\frac{100}{(220)(0.5)} 	imes 100=90.9 \%$\