Two long conductors, separated by a distance $d$ carry currents $I_1$ and $I_2$ in the same direction. They exert a force $F$ on each other. Now the current in one of them is increased to two times and its direction is reversed. The distance is also increased to $3d$. The new value of the force between is them is

A coil of $100$ turns is lying in a magnetic field of $1 \mathrm{T}$ as shown in the figure. A current of $1 \mathrm{A}$ is flowing in this coil. The torque acting on the coil will be

Four wires of equal length are bent in the form of four loops $P, Q, R$ and $S.$ These are suspended in a uniform magnetic field and same current is passed in them. The maximum torque will act on.