Question

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

$
P _{\text {in }}= I _{ p } V _{ p } \Rightarrow T _{ p }=\frac{ P _{ in }}{ V _{ p }}=\frac{3000 W }{200 N }=15 A
$
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{6 V _{ s }}{3000} $
$V _{ s }=\frac{90 \times 5000}{100 \times 6}=450 V $