Question

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

Answer 1

Correct Answer - A
`X/Y = (20)/(80) =1/4`
`:. Y = 4X`
Since, `(4X)/Y= l/(100-l)`
`:. (4X)/(4X) =l/(100-l)`
`:. 2l = 100`
`:. l = 50 cm`.