Alternating Current - Result Question 37
39. A transformer is used to light a $100 W$ and $110 V$ lamp from a $220 V$ mains. If the main current is $0.5 amp$, the efficiency of the transformer is approximately
[2007]
(a) $50 %$
(b) $90 %$
(c) $10 %$
(d) $30 %$.
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Answer:
Correct Answer: 39. (b)
Solution:
- (b) Efficiency of the transformer
$\eta=\frac{P _{\text{output }}}{P _{\text{input }}} \times 100=\frac{100}{220 \times 0.5} \times 100=90.9 %$
