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Question: Answered & Verified by Expert
A transformer is used to light a $100 \mathrm{~W}$ and $110 \mathrm{~V}$ lamp from a $220 \mathrm{~V}$ mains. If the main current is $0.5 \mathrm{amp}$, the efficiency of the transformer is approximately.
PhysicsAlternating CurrentJEE Main
Options:
  • A $50 \%$
  • B $90 \%$
  • C $10 \%$
  • D $30 \%$
Solution:
1675 Upvotes Verified Answer
The correct answer is: $90 \%$
The efficiency of transformer
$\begin{aligned}
\eta & =\frac{V_s I_s}{V_p I_p} \times 100 \\
& =\frac{100}{220 \times 0.5} \times 100=90 \%
\end{aligned}$

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