Question

The emf of a cell is balanced by a length of 120 cm of a potentiometer wire. When the cell is shunted by a resistance of 10 Ω, the balancing length is reduced by 20 cm. Find the internal resistance of the cell.

Answer 1

Data: R = 10 Ω, l₁ =120 cm,l₂ = 120 - 20 = 100 cm

r = `"R"(("l"_1 - "l"_2)/"l"_2)`

`= 10 ((120 - 100)/100)`

= 2 Ω

The internal resistance of the cell is 2 Ω.