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 where will be the new position of the null point from the same end, if one deicdes to balance a resistance of 4 X against Y

Options

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

Answer

C

Explanation

`(R_1)/( R_2) =(l_1)/( l_2)` where `l_2 = 100 -l_(1)`
In the first case `(X)/( Y)=(20)/(80)`
In the second case
`(4X)/(Y)= (l)/(100-l) rArr l= 50`