Q.

A galvanometer having coil resistance 10Ω shows a full scale deflection for a current of 3 mA. For it to measure a current of 8A, the value of the shunt should be:    [2024]

1 3×10-3Ω  
2 4.85×10-3Ω  
3 3.75×10-3Ω  
4 2.75×10-3Ω  

Ans.

(3)

Given G=10Ω, Ig=3 mA and I=8A

In case of conversion of galvanometer into ammeter.

We have IgG=(I-Ig)S

S=IgGI-Ig=(3×10-3)×108-0.003=3.75×10-3Ω