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 $ \begin{array}{l} i_{g}=\frac{ PD \text { across galvanometer }}{\text { resistance of galvanometer }} \\ i_{g}=\frac{100 \times 10^{-3}}{100 \Omega}=10^{-3} A \end{array} $ 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 $