A galvanometer of resistance $50 \Omega$ is converted to an ammeter. After shunting, the effective…
A galvanometer of resistance $50 \Omega$ is converted to an ammeter. After shunting, the effective resistance of ammeter is $2.5 \Omega$. The value of shunt is
$\frac{100}{19} \Omega$
$\frac{50}{19} \Omega$
$\frac{25}{19} \Omega$
$\frac{75}{19} \Omega$
Solution
The resistance of the galvanometer and the shunt are in parallel. Their equivalent resistance is given by
$\begin{aligned}
& \frac{1}{\mathrm{R}}=\frac{1}{\mathrm{G}}+\frac{1}{\mathrm{~S}} \\
& \therefore \frac{1}{\mathrm{~S}}=\frac{1}{2.5}-\frac{1}{50}=\frac{19}{50}
\end{aligned}$
Or $\mathrm{S}=\frac{50}{19} \Omega$
.