A cell of emf ‘E’ and internal resistance ‘r’ is connected across… - Vidyadip

Question

A cell of emf ‘E’ and internal resistance ‘r’ is connected across a variable resistor ‘R’. Plot a graph showing the variation of terminal potential ‘V’ with resistance R. Predict from the graph the condition under which ‘V’ becomes equal to ‘E’.

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Answer

$\text{V} = \text{IR} = \frac{\text{ER}}{\text{R}+ \text{r}}= \frac{\text{E}}{\frac{\text{r}}{\text{R}}+ 1}$

When R approaches infinity (or for $\text{R}\to\infty$) V becomes equal to E.

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