Question

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

• A. $\text{50 A}$
• B. $\text{25 A}$
• C. $\text{45 A}$
• D. $\text{35 A}$

Answer 1

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

Efficiency, $\eta =\frac{P_{out}}{P_{in}}=\frac{V_s{I}_s}{V_p{I}_p}$
$\Rightarrow 0.9=\frac{230\times I_s}{2300\times 5}$
$\Rightarrow I_s=0.9\times 50=45\text{A}$
Output current $=45\text{A}$