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Question: Answered & Verified by Expert
A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the current is 0.5 A, the efficiency of the transformer is
PhysicsAlternating CurrentJEE Main
Options:
  • A 86%
  • B 91%
  • C 96%
  • D 98%
Solution:
1189 Upvotes Verified Answer
The correct answer is: 91%
Given: Output power, P=100 W

The voltage across the primary coil, Vp=220 V

Current in the primary coil, Ip=0.5 A

The efficiency of a transformer, η = output power input power × 1 0 0

=PVpIp×100=100220×0.5×10091%

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