Question

A moving coil galvanometer of resistance $100$ ohm gives a full scale deflection of $50$ divisions for a current of $20$ ampere. How will you convert it into an ammeter to read $1$ ampere for $100$ divisions?

Answer 1

A shunt resistance (S) need to be connected to galvanometer in

parallel to convert into ammeter.

galvanometer resistance = 100

I(g) = 20 A

1 A for 100 th division.

So for 50 divisions it will be 100 A.

So we need to make ammeter of 0 - 100 A

I = 100 A

S = $\frac{I\left(g\right)\times G}{(I-I(g\left)\right)}$

S = $\frac{20\times 100}{(100-20)}$

S = $\frac{200}{80}$

S = 2.5 Ohm