question_answer

A galvanometer of resistance 240\[\Omega \] allows only 4% of the main current after connecting a shunt resistance. The value of the shunt resistance is

A)  10\[\Omega \]            

B)  20\[\Omega \]

C)  8\[\Omega \]             

D)  5\[\Omega \]

Correct Answer: A

Solution :

Given, galvanometer resistance\[G=240\Omega \]Shunt resistance S = ? \[{{I}_{G}}=\frac{4}{100}I\] From figure voltage through the circuit. \[(I-{{I}_{G}})S={{I}_{G}}G\] or \[\left( 1-\frac{4I}{100} \right)S=\frac{4I}{100}\times 240\] or \[S=\frac{4\times 240}{96}=10\Omega \]