Question

A galvanometer of resistance $20\Omega$ is to be converted into an ammeter of range $1A$. If a current of $1mA$ produces full-scale deflection, the shunt required for the purpose is

• A. $0.01\Omega$
• B. $0.05\Omega$
• C. $0.02\Omega$
• D. $0.04\Omega$

Answer 1

The correct option is C $0.02\Omega$

Given, $R_G=20\Omega i=1A{i}_g=1mA$
here, $(i-i_g)R_s=i_g{R}_G$
$R_s=\frac{i_g{R}_G}{(i-i_g)R_s}$
using the given values,

$R_s=\frac{1mA\times 20}{1-0.001}=0.02\Omega$