For the situation shown in figure, find the force experienced by side $MN$ of the rectangular loop. Also, find the torque on the loop.

 

$$\begin{gathered} \frac{F}{L}=\frac{{\mu }_0}{2\mathrm{\pi }}\frac{I_1{I}_2}{a} \\ \therefore F=\frac{{\mu }_0}{2\mathrm{\pi }}\frac{I_1{I}_2}{a}L \end{gathered}$$

It will be repulsion or upwards

$M$ of the loop is inwards and magnetic field to $I_1$ on the plane of loop is outwards. Hence, $\tau =0$, as $\tau =M\times B$ and the angle between the two is $180°$.