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Question: Answered & Verified by Expert
In a potentiometer experiment, the balancing length for a cell $240 \mathrm{~cm}$. On shunting the cell with a resistance of $2 \Omega$, the balancing length become half the initial balancing length. The internal resistance of the cell is
PhysicsCurrent ElectricityMHT CETMHT CET 2021 (22 Sep Shift 2)
Options:
  • A $1.5 \Omega$
  • B $1 \Omega$
  • C $0.5 \Omega$
  • D $2 \Omega$
Solution:
2843 Upvotes Verified Answer
The correct answer is: $2 \Omega$
The internal resistance is given by
$$
\begin{aligned}
& r=R\left(\frac{\ell_1-\ell_2}{\ell_2}\right) \\
& =2\left(\frac{240-120}{120}\right)=2 \Omega
\end{aligned}
$$

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