Question

A power transmission line feeds input power at $2400 \, V$ to a step-down transformer which delivers power at $240 \, V$ with its primary windings having $5000$ turns. If the current in the primary coil of the transformer is $5 \, A$ and its efficiency is $80\%,$ then what is the output current (in $A$ )?

Answer 1

$\epsilon _{p}=2400V,N_{p}=5000$
$\epsilon _{s}=240V,I_{p}=5A$
$\eta=80\%=0.8$
$\eta=\frac{P_{out}}{P_{in}}=\frac{\epsilon _{s} I_{s}}{\epsilon _{p} I_{p}}$
$\Rightarrow I_{s}=\frac{\eta \epsilon _{p} I_{p}}{\epsilon _{s}}=\frac{0 . 8 \times 2400 \times 5}{240}=40A$