Question

A galvanometer has a resistance of $100\, \Omega$. A potential difference of $100 \,mV$ between its terminals gives a full scale deflection. The shunt resistance required to convert it into an ammeter reading upto $5 \,A$ is

• A. $0.01\, \Omega $
• B. $0.02\,\Omega $
• C. $0.03\,\Omega $
• D. $0.04\, \Omega $

Answer 1

Answer: (B)

The current required for full-scale deflection is
$i_{g}=\frac{\text { PD across galvanometer }}{\text { resistance of galvanometer }}$
$i_{g}=\frac{100 \times 10^{-3}}{100 \Omega}=10^{-3} A$

The shunt resistance required is
$S=\left(\frac{i_{g}}{i-i_{g}}\right) G=\left(\frac{10^{-3}}{5-10^{-3}}\right) \times 100=0.02\, \Omega$