Question

In the potentiometer experiment, the balancing length with a cell E₁ of unknown e.m.f. is 'ℓ₁' cm. By shunting the cell with resistance R Ω, the balancing length becomes `ℓ_1/2` cm, the internal resistance (r) of a cell is ______

पर्याय

• r = 2R 

• r = 0

• r = `R/2`

• r = R

Answer 1

In the potentiometer experiment, the balancing length with a cell E₁ of unknown e.m.f. is 'ℓ₁' cm. By shunting the cell with resistance R Ω, the balancing length becomes `ℓ_1/2` cm, the internal resistance (r) of a cell is r = R.

Explanation:

r = `R(ℓ_1/ℓ_2 - 1)     ℓ_2 = ℓ_1/2`

Putting the values and solving we get

r = R