Q 12-03-184JEE MainJEE Main 2022 (27 Jul, Shift 2)Easy
In a meter bridge experiment with resistances $R_1$ and $R_2$ in the two gaps, the balancing length $AC$ corresponding to null deflection of the galvanometer is $40$ cm. The balancing length, if the radius of the wire $AB$ is doubled, will be ______ cm.
Numerical value type. Enter your answer.
Answer: 40
At balance $\dfrac{R_1}{R_2} = \dfrac{l}{100 - l}$. The wire is uniform, so this ratio of lengths does not depend on the wire's radius.
Doubling the radius changes the resistance per cm equally everywhere, so the balancing length stays $40$ cm.
Solution by Sreeraj P, M.Sc Physics