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Question: Answered & Verified by Expert
Two identical cells each of emf $\mathrm{E}$ and internal resistance $\mathrm{r}$ are connected in parallel with an external resistance $\mathrm{R}$. To get maximum power developed across $R$, the value of $R$ is
PhysicsCurrent ElectricityWBJEEWBJEE 2009
Options:
  • A $R=r / 2$
  • B $\mathrm{R}=\mathrm{r}$
  • C $R=r / 3$
  • D $\mathrm{R}=2 \mathrm{r}$
Solution:
1581 Upvotes Verified Answer
The correct answer is: $R=r / 2$
$R_{e q}=\frac{r}{2}$
$I=\frac{2 E}{r+2 R}$
For max. power consumption. I should be max. So denominator should be min. for that
$r+2 R=(\sqrt{r}, \quad)$

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