Question

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

• A. $.25\Omega$
• B. $.4\Omega$
• C. $.5\Omega$
• D. $4\Omega$

Answer 1

The correct option is A $.25\Omega$

$L=20cm$

$R_{AP}=1\Omega$

Let the unknown resistance be $R$.

$\frac{R_{A}P}{R_{P}B}=\frac{100-L}{L}$

$R=\frac{R_{AP}\times L}{100-L}$

$=\frac{1\times 20}{80}$

$=\frac{1}{4}$

$=0.25\Omega$