Why is the magnetic field radial in a moving coil galvanometer? Explain how it is achieved.

The magnitude F of the force between two straight parallel current carrying conductors kept at a distance d apart in air is given by $F=\frac{{\mu }_0}{2\pi }\frac{I_1{I}_2}{d}$, where $I_1$ and $I_2$ are the currents flowing through the two wires. Use this expression, and the sign convention that the: "Force of attraction is assigned a negative sign and force of repulsion is assigned a positive sign". Draw graphs showing dependence of $F$ on

(i) $I_1{I}_2$ when $d$ is kept constant.

The magnitude F of the force between two straight parallel current carrying conductors kept at a distance d apart in air is given by $F=\frac{{\mu }_0}{2\pi }\frac{I_1{I}_2}{d}$, where $I_1$ and $I_2$ are the currents flowing through the two wires. Use this expression, and the sign convention that the: "Force of attraction is assigned a negative sign and force of repulsion is assigned a positive sign". Draw graphs showing dependence of $F$ on

(ii) $d$ when the product $I_1{I}_2$ is maintained at a constant positive value.

The magnitude F of the force between two straight parallel current carrying conductors kept at a distance d apart in air is given by $F=\frac{{\mu }_0}{2\pi }\frac{I_1{I}_2}{d}$, where $I_1$ and $I_2$ are the currents flowing through the two wires. Use this expression, and the sign convention that the: "Force of attraction is assigned a negative sign and force of repulsion is assigned a positive sign". Draw graphs showing dependence of $F$ on

(ii) $d$ when the product $I_1{I}_2$ is maintained at a constant negative value.