Question

An unknown resistance is placed in the left gap and resistance of $50$ohm is placed in the right gap of a meter bridge. The null point is obtained at $40$cm from the left end. Determine the unknown resistance.

Answer 1

Let the unknown resistance placed in the left gap be $P$. Known resistance in the right gap $R=50\Omega$

Null point is obtained at $40$ cm i.e. $l=40$ cm

Using balanced Wheatstone bridge equation $\frac{P}{R}=\frac{l}{100-l}$

$\therefore$ $\frac{P}{50}=\frac{40}{100-40}$

We get $P=33.33\Omega$