Question

A galvanometer has a resistance G and a current flowing in it produces full scale deflection. $S_1$ is the value of the shunt, which converts it into an ammeter of range $0-I$ and $S_2$ is the value of the shunt for the range $0-2I$. The ratio is

• A. 2
• B. 1
• C. \frac{S_1}{S_2}$$=$$\begin{pmatrix}\frac{2I-I_g}{I-I_g}\end{pmatrix}
• D. \frac{S_1}{S_2}$$=$$\frac{1}{2}$$\begin{pmatrix}\frac{I-I_g}{2I-I_g}\end{pmatrix}

Answer 1

Answer: (C)

\frac{S_1}{S_2}$$=$$\begin{pmatrix}\frac{2I-I_g}{I-I_g}\end{pmatrix}

Answer 2

The correct answer is C:$\frac{S_1}{S_2} = \frac{(2I - I_g)}{(I - I_g)}$
Using S = $I_g G/(I - I_g)$
Using the above equation;
⇒$S_1=\frac{i_gG}{(I-i_g)}$
⇒$S_2=\frac{i_gG}{(2I-i_g)}$
we get $\frac{S_1}{S_2} = \frac{(2I - I_g)}{(I - I_g)}$
This is the proper form of the given expressions and their ratio.