Question

A galvanometer of resistance 5$\Omega$ is connected in series with a resistance of 0.2 $\Omega$ to a battery of negligible internal resistance. The deflection is noted. If the 0.2 $\Omega$ resistance is replaced by 2 $\Omega$ resistance, the value of shunt resistance to be connected to the galvanometer to maintain the same deflection is

• A. 1$\Omega$
• B. 8.9$\Omega$
• C. 0.01$\Omega$
• D. 10$\Omega$

Answer 1

Answer: (B)

8.9$\Omega$

$G=5\Omega ,R=0.2\Omega$

$I=\frac{V}{5+0.2}$

$\text{Now}0.2\Omega \text{is replaced by}2\Omega$

$I=\frac{V}{\frac{5S}{5+S}+2}$

$\Rightarrow 5+0.2=\frac{5S}{5+S}+2$

$\Rightarrow 3.2=\frac{5S}{5+S}$

$\Rightarrow 16+3.2S=5S$

$\Rightarrow S=\frac{16}{1.8}=\frac{8}{0.9}=8.9\Omega$