Question

A step down transformer transforms a supply line voltage of 2200 V into 220 V. The primary coil has 4000 turns. The efficiency of transformer is 80% and power output is 8 kW, then power supplied is
(1) 10 kW
(2) 8 kW
(3) 6 kW
(4) 5 kW

Answer 1

$$\begin{gathered} efficiency=\frac{poweroutput}{powerinput} \\ \frac{80}{100}=\frac{8\times 1000}{P_{in}} \\ {P}_{in}=10kW \end{gathered}$$