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Question: Answered & Verified by Expert
The maximum power drawn out of the cell from a source is given by (where $r$ is internal resistance)
PhysicsCurrent ElectricityJEE Main
Options:
  • A $E^2 / 2 r$
  • B $E^2 / 4 r$
  • C $E^2 / r$
  • D $E^2 / 3 r$
Solution:
2653 Upvotes Verified Answer
The correct answer is: $E^2 / 4 r$
$i=\frac{E}{r+R} \Rightarrow P=i^2 R \Rightarrow P=\frac{E^2 R}{(r+R)^2}$
Power is maximum when $r=R \Rightarrow P_{\text {max }}=E^2 / 4 r$

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