Question

A transformer of efficiency $90\%$ has turns ratio $10:1.$ If the voltage across the primary is $220 V$ and current in the primary is $0.5 \, A,$ then the current in secondary is

• A. $5.5 \, A$
• B. $5 \, A$
• C. $4 \, A$
• D. $4.5 \, A$

Answer 1

Answer: (D)

Given, $\frac{N_{P}}{N_{S}}=\frac{10}{1}$
$V_{P}=220 \, V, \, I_{P}=0.5 \, A$
We know that, $\frac{V_{P}}{V_{S}}=\frac{N_{P}}{N_{S}}$
Efficiency, $\eta=\frac{O u t p u t \, p o w e r}{I n p u t \, p o w e r}=\frac{I_{S} V_{S}}{I_{P} V_{P}}$
$\frac{90}{100}=\frac{I_{S}}{0.5}$ $\times \frac{1}{10}$
$\Rightarrow \, \, I_{S}=4.5 \, A$