question_answer

In a circuit 5% of total current passes through a galvanometer.   If   resistance   of   the galvanometer is G, then value of the shunt is:

A)  19 G          

B)  20 G

C)  G/20        

D)  G/19

Correct Answer: D

Solution :

 Key Idea: Potential difference across galvanometer and shunt is same. Let \[{{i}_{g}}\]current passes through galvanometer, and \[i-{{i}_{g}}\]through shunt S, then \[{{i}_{g}}G=(i-{{i}_{g}})S\] \[S=\left( \frac{{{i}_{g}}}{i-{{i}_{g}}} \right)G\] Given, \[{{i}_{g}}=5A,\,i=100A,\] \[\therefore \] \[S=\left( \frac{5}{100-5} \right)G=\frac{G}{19}\]