Question

A transformer having efficiency of $90\%$ is working on $200V$ and $3kW$ power supply. If the current in the secondary coil is $6A$, the voltage across the secondary coil and the current in the primary coil respectively are

• A. 300 V, 15 A
• B. 450 V, 15 A
• C. 450 V, 13.5 A
• D. 600 V, 15 A

Answer 1

Answer: (B)

$<br/>P_{\text{in }}=I_p{V}_p\Rightarrow T_p=\frac{P_{in}}{V_p}=\frac{3000W}{200N}=15A<br/>$
Efficciency of the transformer
$\eta =\frac{P_{\text{out }}}{P_{\text{in }}}=\frac{V_s{I}_s}{V_{p_1}{I}_p}\Rightarrow$
$\frac{90}{100}=\frac{6V_s}{3000}$
$V_s=\frac{90\times 5000}{100\times 6}=450V$