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JEE Main 2020 (7 Jan, Shift 2) · Potentiometer

Potentiometer question from JEE Main 2020 (7 Jan, Shift 2)

Q68JEE Main 2020 · 7 JAN · SHIFT 2Medium

Potentiometer

The balancing length for a cell is 560 cm in a potentiometer experiment. When an external resistance of 10 $\Omega$ is connected in parallel to the cell, the balancing length changes by 60 cm. If the internal resistance of the cell is $\frac{N}{10}\ \Omega$ , where N is an integer then value of N is .............

Numerical answer type. Work it out, then open the answer.

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Answer: 12

Shunting reduces the length: $l = 560-60 = 500$ cm.
$r = R\dfrac{l_0-l}{l} = 10\times\dfrac{60}{500} = 1.2\ \Omega$
$\dfrac{N}{10} = 1.2 \Rightarrow N = 12$

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