question_answer

A galvanometer of resistance \[50\Omega \] gives a full scale deflection for a current \[5\times {{10}^{-4}}A\]. The resistance that should be connected in series with the galvanometer to read 3 V is

A)  \[5050\Omega \]          

B)  \[5950\Omega \]

C)  \[595\Omega \]

D)  \[5059\Omega \]

Correct Answer: B

Solution :

: Here, Resistance of galvanometer, \[G=50\Omega \]. Current for full scale deflection, \[{{I}_{g}}=5\times {{10}^{-4}}A\] Let R be resistance connected in series with the galvanometer to read 3 V. Then \[V={{I}_{g}}(G+R)\] or \[R=\frac{V}{{{I}_{g}}}-G\] \[R=\frac{3V}{5\times {{10}^{-4}}}-50\Omega \] \[=6000\Omega -50\Omega =5950\Omega \]