Question

In a potentiometer circuit a cell of EMF 1.5 V gives balance point at 36 cm length of wire. If another cell of EMF 2.5 V replaces the first cell, then at what length of the wire, the balance point occurs?

(1) 60 cm 

(2) 21.6 cm 

(3) 64 cm 

(4) 62 cm

Answer 1

Correct option is (1) 60 cm

From the application of potentiometer to compare two cells of emfs E₁ and E₂ by balancing lengths l₁ and l₂.

\(\frac{E_1}{E_2} = \frac{l_1}{l_2}\)

⇒ \(l_2 = l_1\left(\frac{E_2}{E_1}\right)\)

\(= 36 \left(\frac{2.5V}{1.5V}\right)\)

\(= 60 \) cm

Answer 2

Option : (1) 60 cm