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 $'R'$ 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 $\frac{5}{R / 2}=\frac{1 . 6 \ell _{1}}{100 - 1 . 6 \ell _{1}}$
$\Rightarrow R=15\Omega$