In a meter bridge experiment, 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 the new position of the null point from the same end, if one decides to balance a resistance of `4 X` against `Y` will be at.

Options

A. 50 cm
B. 80 cm
C. 40 cm
D. 70 cm

Answer

A

Explanation

`(X)/(Y) = (20)/(100 - 20) rArr 4 X = Y`
`(4 X)/(Y) = (l)/(100 -l) rArr 1 = (l)/(100 - l)`
`l = 50 cm`.