Question

As shown in the figure initially switch $k_{1}$ is open and $k_{2}$ is closed and deflection of galvanometer is $\theta _{0}$ . Now both switch are closed then the deflection in galvanometer is (given $R_{H}=5\text{\Omega }$ )

• A. $24 \, \Omega$
• B. $22\Omega$
• C. $42\Omega$
• D. $50\Omega$

Answer 1

Answer: (B)

$\theta _{0} \propto i_{G}\Rightarrow C\theta _{0}=i_{G}$
I-case $C\theta _{0}=\frac{v}{220 + R}$ ......(1)
II-case $C\frac{\left(\theta \right)_{0}}{5}\frac{v}{\left(220 + \frac{5 R}{5 + R}\right)}\times \frac{5}{5 + R}$ ..........(2)
From (1) and (2) $R=22\Omega$