A moving coil galvanometer of resistance $G$ gives a full scale deflection for a current $I_g$ Use the suitable circuit diagram to convert it into an ammeter of range $0$ to $I\left(I>I_g\right)$. Deduce the expression for the shunt required for this conversion. Hence write the expression for the resistance of the ammeter thus obtained.

Three long straight parallel wires are kept as shown in Figure. The wire $\left(3\right)$(3) carries a current $I$. The direction of flow of current $I$ in wire $\left(3\right)$, is such that the net force, on wire $\left(1\right)$, due to the other two wires is zero.

Three long straight parallel wires are kept as shown in Figure. The wire $\left(3\right)$(3) carries a current $I$. By reversing the direction of $I$, the net force, on wire $\left(2\right)$, due to the other two wires, becomes zero. What will be the directions of current $I$, in the two cases? Also, obtain the relation between the magnitudes of currents $I_1, I_2$and $I$.