Question

A galvanometer has a coil resistance of $100\Omega$. It gives a full scale deflection when a current of 0.001 A is passed through it. The, value of resistance which can convert the galvanometer into an ammeter giving full scale deflection for a current of $10A$ is :

• A. ${10}^{-4}\Omega$
• B. ${10}^{-2}\Omega$
• C. ${10}^4\Omega$
• D. ${10}^2\Omega$

Answer 1

Answer: (B)

${10}^{-2}\Omega$

$S=\frac{i_{g}G}{i-i_g}$

$S=\frac{\left({10}^{-3}A\right)\left(100\right)}{(10-{10}^{-3})A}=\frac{0.1}{999}\approx {10}^{-2}\Omega$