question_answer

A \[36\,\Omega \]galvanometer is shunted by resistance of \[4\,\Omega .\] The percentage of the total current,   which   passes   through   the galvanometer is

A)  8%           

B)  9%

C)  10%          

D)  91%

Correct Answer: C

Solution :

 Let G be resistance of galvanometer and \[{{i}_{g}}\]the current which on passing through the galvanometer produces full scale deflection. If \[i\] is the maximum current, and since, G and S are in parallel. \[{{i}_{g}}\times G=(i-{{i}_{g}})\times S\] \[\Rightarrow \] \[\frac{{{i}_{g}}}{i}=\frac{S}{S+G}\] Given, \[G=36\,\Omega ,\,S=4\Omega \] \[\therefore \] \[\frac{{{i}_{g}}}{i}=\frac{4}{36+4}=\frac{4}{40}\] \[\Rightarrow \] \[{{i}_{g}}=\frac{i}{10}\] \[\therefore \] \[1000\times \frac{{{i}_{g}}}{i}=\frac{1}{10}\times 100\] \[\Rightarrow \] \[\frac{{{i}_{g}}}{i}%=10%\]