In a meter bridge experiment null point is obtained at 20 cm from one end when resistance X is balanced against resistance Y, where X < Y. Then, the new position of the null point from the same end if X is replaced by 4X will be
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 50 cm
formula for Null point,
$\frac{x}{y}=\frac{l}{100-l}$
Case 1: $\frac{x}{y}=\frac{20}{100-20}=\frac{1}{4}$
Case 2: $x=4x$
$\frac{4x}{y}=\frac{l'}{(100-l')}=4(\frac{x}{y})=\frac{1}{4}$
$⇒\frac{l'}{100-l'}=1$
$⇒l'=50cm$