Question

To send 10% current through the coil of galvanometer of resistance 18 ohm, what is the required shunt resistance?

Answer 1

Let I be the total current in the circuit.
The current through the galvanometer, I_g = 10% of I = 0.1I
The galvanometer resistance, G = 18 Ω
Let S be the shunt resistance.
The current through the galvanometer is given as;
$$\begin{gathered} I_g=I\left(\frac{G}{G+S}\right) \\ \Rightarrow 0.1I=I\left(\frac{18}{18+S}\right) \\ \Rightarrow 18+S=\frac{18}{0.1}=180 \\ \Rightarrow S=180-18=162\Omega \end{gathered}$$