Question

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. $20\Omega$
• B. $8\Omega$
• C. $5\Omega$
• D. $10\Omega$

Answer 1

Answer: (D)

Given, galvanometer resistance $G=240\Omega$

Shunt resistance $S=?$
$I_G=\frac{4}{100}I$
From figure voltage through the circuit.
$\left(I-I_G\right)S=I_{G}G$
or $\left(1-\frac{4I}{100}\right)S=\frac{4I}{100}\times 240$
or $\S =\frac{4\times 240}{96}=10\Omega$