A cell in the secondary circuit gives null deflection for 2.5 m length of a potentiometer having 10m length of wire. If the length of the potentiometer wire is increased by 1m without changing the cell in the primary, the position of the null point wil be

Options

A. 3.5 m
B. 3 m
C. 2.75 m
D. 2.0 m

Answer

C

Explanation

`l = 2.5 cm`
Since, `L prop l`
`rArr L_(1)/L_(2) = l_(1)/l_(2) rArr 10/11 = 2.5/l_(2) rArr l_(2) = (2.5 xx 11)/10 = 2.75 m`