A power transmission line feeds input power at 2400 V to a step-down transformer with its primary windings having 5000 turns. The output power is delivered at 240 V by the transformer. If the current in the primary coil of the transformer is 5 A and its efficiency is 95% then the current in the secondary will be
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( 47.5\,\mathrm{A} \)
The efficiency of a transformer is the output power divided by the input power. The number of turns is not needed.
\( \displaystyle P_{\mathrm{in}} = V_{p} I_{p} = 2400 \times 5 = 12000\,\mathrm{W} \)
Efficiency 95% means \( \eta = 0.95 \).
\( \displaystyle P_{\mathrm{out}} = \eta\,P_{\mathrm{in}} = 0.95 \times 12000 = 11400\,\mathrm{W} \)
\( \displaystyle I_{s} = \frac{P_{\mathrm{out}}}{V_{s}} = \frac{11400}{240} = 47.5\,\mathrm{A} \)