Question

A cell, shunted by a 8Ω resistance, is balanced across a potentiometer wire of length 3m. The balancing length is 2 m when the cell is shunted by 4Ω resistance. The value of internal resistance of the cell will be _____ Ω.

Answer 1

Correct answer is 8

Answer 2

Correct answer: 8

\(\frac{\varepsilon_1 8}{r_1 + 8} = 3c\)

\(\frac{\varepsilon_1 4}{r_1 + 4} = 2c\)

⇒ \(\frac{2(r_1 + 4)}{r_1 + 8} = \frac 32\)

⇒ \(r_1 = 8 \Omega\)