In the given circuit of potentiometer, the potential difference E… | JEE Main 2021 (25 Feb, Shift 1)

Q57JEE Main 2021 · 25 FEB · SHIFT 1Medium

Potentiometer

In the given circuit of potentiometer, the potential difference E across AB (10 m length) is larger than E1 and E2 as well. For key K1 (closed), the jockey is adjusted to touch the wire at point J1 so that there is no deflection in the galvanometer. Now the first battery (E1) is replaced by second battery (E2) for working by making K1 open and K2 closed. The galvanometer gives then null deflection at J2. The value of $\frac{E_1}{E_2}$ is $\frac{a}{b}$ , where a = _________.

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

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Answer: 1

The wire is 10 rows of 1 m each, folded; odd rows run left to right from A, even rows run right to left.
$J_1$ is on row 4 (runs right to left), 20 cm from its left end: $AJ_1 = 3\text{ m} + 80\text{ cm} = 380$ cm.
$J_2$ is on row 8 (runs right to left), 60 cm from its right end: $AJ_2 = 7\text{ m} + 60\text{ cm} = 760$ cm.
$\dfrac{E_1}{E_2} = \dfrac{AJ_1}{AJ_2} = \dfrac{380}{760} = \dfrac{1}{2}$
So $a = 1$ .

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Potentiometer question from JEE Main 2021 (25 Feb, Shift 1)

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