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,   \[{{i}_{g}}=5A,\,\,100\,\,A,\] \[\therefore \]  \[S=\left( \frac{5}{100-5} \right)G=\frac{G}{19}\]