question_answer

We have a galvanometer of resistance \[25\,\Omega .\] It is shunted by a \[2.5\,\Omega \] wire. The part of total current that flows through the galvanometer is

A) \[\frac{I}{{{I}_{{}^\circ }}}=\frac{2}{11}\]     

B)        \[\frac{I}{{{I}_{{}^\circ }}}=\frac{1}{11}\]

C) \[\frac{I}{{{I}_{{}^\circ }}}=\frac{4}{11}\]     

D)        \[\frac{I}{{{I}_{{}^\circ }}}=\frac{3}{11}\]

Correct Answer: B

Solution :

[b] \[I'=\frac{{{I}_{0}}\times 2.5}{(25+25)}={{I}_{0}}\times \frac{25}{275}=\frac{1}{11}\times {{I}_{0}}\] \[\Rightarrow \] \[\frac{I'}{{{I}_{0}}}=\frac{1}{11}.\]