Question

A power transmission line feeds input power at $2300\text{V}$ to a step-down transformer with its primary windings having $4000$ turns. The output power is delivered at $230\text{V}$ by the transformer. If the current in the primary coil of the transformer is $5\text{A}$ and its efficiency is $90\%.$ The output current would be

• A. $45\text{A}$
• B. $30\text{A}$
• C. $15\text{A}$
• D. $20\text{A}$

Answer 1

The correct option is A $45\text{A}$

Efficiency of a transformer is given by

$\eta =\frac{P_{out}}{P_{in}}=\frac{V_S{I}_S}{V_P{I}_P}$

$\Rightarrow 0.9=\frac{230\times I_S}{2300\times 5}$

$\Rightarrow I_S=0.9\times 50=45\text{A}$

$\therefore$ Output current $=45\text{A}$

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(A\right)$ is the correct answer.