Question

A galvanometer having resistance of $50\Omega$ requires a current of $100\mu A$ to give full scale deflection. How much resistance is required to convert it into an ammeter of range of $10A$?

• A. $5\times {10}^{-3}\Omega$ in series
• B. $5\times {10}^{-4}\Omega$ in parallel
• C. ${10}^5\Omega$ in series
• D. ${10}^5\Omega$ in parallel

Answer 1

Answer: (B)

$5\times {10}^{-4}\Omega$ in parallel

To convert a galvanometer into an ammeter, a resistance (shunt) is required, connected in parallel to the galvanometer.
By using,
$S=\frac{Gi}{i-i_g}=\frac{50\times 100\times {10}^{-6}}{(10-100\times {10}^{-6})}$
$=5\times {10}^{-4}\Omega$.