Physics - Current Electricity Question with Solution | TestHub

Key Idea : Potential difference across galvanometer should be equal to potential difference across shunt. The shunt and galvanometer are connected as shown in figure.Let total current through the parallel combination is $i$, the current through the galvanometer is $i_g$ and the current through the shunt is $i-i_g$. The potential difference $V_{ab}\left(=V_a-V_b\right)$ is the same for both paths, so $\begin{array}{ll}& i_{g}G=\left(i-i_g\right)S\\ \text{ or }& i_g(G+S)=iS\\ \text{ or }& \frac{i_g}{i}=\frac{S}{S+G}\end{array}$ The fraction of current passing through shunt $\begin{array}{rl}& =\frac{i-i_g}{i}=1-\frac{i_g}{i}\\ & =1-\frac{S}{S+G}=\frac{G}{S+G}\\ & =\frac{8}{2+8}=\frac{8}{10}\\ & =0.8\mathrm{A}\end{array}$