Question

The resistance in the two arms of a meter bridge are $5\Omega$ and $R\Omega$ respectively. When the resistance $R$ is shunted with an equal resistance, the new balance point is at $1.6{\ell }_1$ . The resistance ${}^{\prime }{R}^{\prime }$ is:

• A. $10\Omega$
• B. $15\Omega$
• C. $20\Omega$
• D. $25\Omega$

Answer 1

Answer: (B)

$\frac{5}{R}=\frac{{\ell }_1}{100-{\ell }_1}$ and $\frac{5}{R/2}=\frac{1.6{\ell }_1}{100-1.6{\ell }_1}$
$\Rightarrow R=15\Omega$