question_answer

What is the value of shunt resistance required to convert a galvanometer of resistance \[100\Omega \] into an ammeter of range 1A? Given: Full scale deflection of the galvanometer is 5 mA.

A)  \[0.5\Omega \]

B)  \[\frac{5}{9.95}\Omega \]

C)  \[0.05\Omega \]

D)  \[\frac{9.95}{5}\Omega \]

Correct Answer: B

Solution :

: Here, Resistance of galvanometer, \[G=100\Omega \] Full scale deflection current, \[{{I}_{g}}=5mA\] \[=5\times {{10}^{-3}}A\] To convert the galvanometer into an ammeter of range 1 A, a shunt resistance of value S is connected in parallel with it such that, \[(I-{{I}_{g}})={{I}_{g}}G\] \[S=\frac{{{I}_{g}}G}{I-{{I}_{g}}}=\frac{5\times {{10}^{-3}}\times 100}{1-5\times {{10}^{-3}}}=\frac{5\times {{10}^{-1}}}{1-0.005}\] \[=\frac{0.5}{0.995}=\frac{5}{9.95}\Omega \]