While finding internal resistance of a cell, a student observes that the balance length is 2m when cell is shunted by $5 Ω$ resistance and balance length is 3m when cell is shunted by $10 Ω$ resistance. Internal resistance of cell is.

see full answer

Talk to JEE/NEET 2025 Toppers - Learn What Actually Works!

Real Strategies. Real People. Real Success Stories - Just 1 call away

An Intiative by Sri Chaitanya

$1.5 Ω$

$1 Ω$

$10 Ω$

$15 Ω$

answer is B.

(Unlock A.I Detailed Solution for FREE)

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Detailed Solution

We know

$l \propto \frac{ER}{R + r}$

$\Rightarrow \frac{l_{1}}{l_{2}} = \frac{R_{1}}{R_{2}} \times \frac{R_{2} + r}{R_{1} + r}$

$\Rightarrow \frac{2}{3} = \frac{5}{10} (\frac{10 + r}{5 + r})$

$\Rightarrow \frac{4}{3} = \frac{10 + r}{5 + r}$

$20 + 4 r = 30 + 3 r \Rightarrow r = 10 Ω$

Watch 3-min video & get full concept clarity

JEE

NEET

Foundation JEE

Foundation NEET

CBSE