Question

A galvanometer with a resistance of 15.0Ω gives a full-scale reading for current of 3.0 A. What shunt resistance is needed to convert this into an ammeter with a 30.Ω A full-scale reading?

Answer 1

We know that

$S=\frac{i_g G}{I-i_g}$

$i_g=\frac{SI}{S+G}$

$i_g=\frac{SI}{S+G}$

Put value

$i_g=\frac{15\times3}{30+15}=1A$