question_answer

A galvanometer has a resistance of 100\[\Omega \]. A potential difference of 100 mV between its terminals gives a full scale deflection. The shunt resistance required to convert it into an ammeter reading upto 5 A is

A) 0.01\[\Omega \]  

B)                                                       0.02\[\Omega \]              

C)       0.03\[\Omega \]              

D)       0.04\[\Omega \]

Correct Answer: B

Solution :

The current required for full-scale deflection is \[{{\text{i}}_{\text{g}}}\text{=}\frac{\text{PD}\,\text{across}\,\text{galvanometer}}{\text{resistance}\,\text{of}\,\text{galvanometer}}\] \[{{\text{i}}_{\text{g}}}\text{=}\frac{100\times {{10}^{-3}}}{100\Omega }={{10}^{-3}}A\] The shunt resistance required is \[S=\left( \frac{{{i}_{g}}}{i-{{i}_{g}}} \right)G=\left( \frac{{{10}^{-3}}}{5-{{10}^{-3}}} \right)\times 100=0.02\Omega \]