In a potentiometer experiment, a cell in the secondary circuit gives null point at text2.5 m when the length of the potentiometer wire is 10 m. If the length of the potentiometer wire is increased by 1 m without changing the cell in the primary circuit, then the position of the null point will be

Question

In a potentiometer experiment, a cell in the secondary circuit gives null point at text2.5 m when the length of the potentiometer wire is 10 m. If the length of the potentiometer wire is increased by 1 m without changing the cell in the primary circuit, then the position of the null point will be (A) 3.5m (B) 3m (C) 2.75 m (D) 2m

Tardigrade Admin · Accepted Answer

The resistance of a potentiometer wire is given as,

R = ρ \times \frac{l}{A}

R^{^{'}} = \frac{2.5 ρ}{A \times 10}

Potential

V^{'} = I \times R^{'}

,

= I {\frac{2.5 ρ}{A \times 10}}

Now, again the length of potentiometer wire is increased by

1 m

, then the resistance of null position wire.

R^{''} = \frac{ρ \times 1}{11 \times A}

V " = I R "

and,

V^{'} = V "

\frac{I \times 2.5 ρ}{A \times 10} = \frac{I \times ρ \times l}{11 \times A}

\frac{2.5 \times 11}{10} = l = 2.75 m

$3.5 m$

$3 m$

$2.75 m$

$2 m$

Q. In a potentiometer experiment, a cell in the secondary circuit gives null point at 2.5m when the length of the potentiometer wire is 10m. If the length of the potentiometer wire is increased by 1m without changing the cell in the primary circuit, then the position of the null point will be

3.5m

3m

2.75m

2m

$3.5 m$

$3 m$

$2.75 m$

$2 m$