Question

A moving coil galvanometer gives a full scale deflection of $30$ when connected in a circuit. When a resistance of $20\Omega$ is connected in parallel with the galvanometer the deflection of the galvanometer reduces to $20$ . What is the resistance of the galvanometer :

• A. $10\Omega$
• B. $20\Omega$
• C. $30\Omega$
• D. $40\Omega$

Answer 1

Answer: (A)

Deflection $\varphi \propto I$
After connection of $20\Omega$ shunt

$20R_g=10\times 20$
$R_g=10\Omega$