Question

In a circuit for finding the resistance of a galvanometer by half deflection method, a $6V$ battery and a high resistance of $11k\Omega$ are used. The figure of merit of the galvanometer $60\mu A/division$. In the absence of shunt resistance, the galvanometer produces a deflection of $\theta =9$ divisions when current flows in the circuit. The value of the shunt resistance that can cause the deflection of $\theta /2$, is closest to

• A. $55\Omega$
• B. $110\Omega$
• C. $220\Omega$
• D. $550\Omega$

Answer 1

The correct option is B $110\Omega$

(i) r is not there.

$I=9\times 60\mu A$

$\frac{6}{11000+G}=540\times {10}^{-6}$

$G=\frac{1000}{9}$

(ii) $G=\frac{RS}{R-S}$

$\frac{1000}{9}=\frac{11000S}{11000-S}$

This gives $S=110$