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NEET 2012 (AIPMT, Mains) · Cells: EMF, Internal Resistance & Combinations

Cells: EMF, Internal Resistance & Combinations question from NEET 2012 (AIPMT, Mains)

Q43NEET 2012 · AIPMT · MAINSEasy

Cells: EMF, Internal Resistance & Combinations

A cell having an emf $\varepsilon$ and internal resistance r is connected across a variable external resistance R. As the resistance R is increased, the plot of potential difference V across R is given by

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Answer: (c)

$V = IR = \frac{\varepsilon R}{R + r} = \frac{\varepsilon}{1 + r/R}$
At $R = 0$ , $V = 0$ ; as $R$ increases $V$ rises and approaches $\varepsilon$ asymptotically (curve bending over).
So the answer is (c).

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