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Question: Answered & Verified by Expert
In meter bridge experiment, null point was obtained at a distance ' $l$ ' from left end. The values of resistances in the left and right gap are doubled and then interchanged. The new position of the null point is
PhysicsExperimental PhysicsMHT CETMHT CET 2023 (10 May Shift 2)
Options:
  • A $(100-l)$
  • B $(100-2 l)$
  • C $(100-3 l)$
  • D $\left(100-\frac{l}{2}\right)$
Solution:
2140 Upvotes Verified Answer
The correct answer is: $(100-l)$
$\begin{aligned}
& \text { For a Metre bridge, } \\
& \frac{\mathrm{X}}{\mathrm{R}}=\frac{l_{\mathrm{X}}}{l_{\mathrm{R}}}
\end{aligned}$
After doubling and interchanging the left and right gap resistances, the ratio of the resistances do not change.
This means the null point does not change.
$\therefore \quad$ The new position will remain at $(100-l)$.

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