In a meter bridge experiment, the null point is obtained at `20 cm`from one end of the wire when resistance `X` is balanced against another resistance `Y`. If `X lt Y`, then where will be the new position of the null point from the same end, if one decides to balanced a resistance of `4X` against `Y`?

Options

A. 30 cm
B. 40 cm
C. 50 cm
D. 60 cm

Answer

C

Explanation

In the first case `l_(1)=20 cm and l_(2)=80 cm [ because l=100 cm]`
`therefore " For balance " (X)/(Y)=(20)/(80)=(1)/(4) or 4 X=Y`
In the second case 4 X=Y as the resistances in the two gaps are equal, the null point will be at the centre or at 50 cm.
`[i.e. (4X)/(Y) " will be " (4X)/(4X)=(l_(1))/(l_(2)) or l_(1)=l_(2)`
`therefore` The null point will be at the centre]