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A transformer is used to light a 140 W, ...

A transformer is used to light a 140 W, 24 V lamp from 240 V AC mains. The current in mains cable is 0.7 A, find the efficiency of transformer.

A

`63.8%`

B

`83.3%`

C

`16.7%`

D

`36.2%`

Text Solution

Verified by Experts

The correct Answer is:
B
Power of source = EI = `240 xx 0.7 = 166`
`Rightarrow` Efficiency = `(140)/(166)` `Rightarrow eta = 83.3 %`
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