Question

In meter bridge the balancing length from left and when standard resistance of $1\Omega$ is in right gap is found to be 20 cm. The value of unknown resistance is

• A. $0.25\Omega$
• B. $0.4\Omega$
• C. $0.5\Omega$
• D. $4\Omega$

Answer 1

The correct option is A $0.25\Omega$


The condition of wheatstone bridge gives $\frac{X}{R}=\frac{20r}{80r}$, r - resistance of wire per cm, X- unknown resistance
$\therefore X=\frac{20}{80}\times R=\frac{1}{4}\times 1=0.25\Omega$