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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

0.9

B

0.8

C

0.7

D

0.6

Text Solution

Verified by Experts

The correct Answer is:
B
`P_(i)=240xx0.7=168W,P_(0)=140W`
`eta=(P_(0))/(P_(i))xx100=(140)/(168)xx100~~80%`
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