Question

In a potentiometer arrangement, a cell of emf 1.25 V gives a balance point at 35 cm length of the wire. If the cell is replaced by another cell and the balance point shifts to 63 cm, what is the emf of the second cell?

Answer 1

Emf of the cell₁, ξ₁ = 1.25 V

Balancing length of the cell, l₁ = 35 cm = 35 x 10^-2 m

Balancing length after interchanged, l₂ = 63 cm = 63 x 10^-2 m

Emf of the cell₁, ξ₂ = ?

The ration of emf’s, `ξ_1/ξ_2 = l_1/l_2`

The ration of emf’s, ξ₂ = ξ₁ = `(l_2/l_1)`

= 1. 25 `xx ((63 xx 10^-2)/(35 xx 10^-2)) = 12.5 xx 1.8` 

ξ₂ = 2.25 V.