question_answer

To find the resistance of galvanometer by the half deflection method the following circuit is used with resistances \[{{\operatorname{R}}_{1}}=9970\Omega ,{{\operatorname{R}}_{2}}=30\Omega \] and \[{{\operatorname{R}}_{3}}=0\]. The deflection in the galvanometer is d. With \[{{\operatorname{R}}_{3}}=107\Omega \]the deflection changed to \[\frac{\operatorname{d}}{2}.\] The galvanometer resistance is approximately:         [JEE ONLINE 22-04-2013]

A)             \[107\Omega \]

B) \[137\Omega \]

C)             \[107/2\Omega \]

D) \[77\,\Omega \]