Define the electromagnetic unit of current.

Two long parallel straight wire $P and Q$ separated by a distance $5 \mathrm{cm}$ in air carry a current of $4\mathrm{A} \mathrm{and} 2\mathrm{A}$respectively in

 the same direction. Find the force acting per cm of wire and indicate the direction of force.

Derive an expression for torque on the rectangular coil of area $\mathrm{A}$ carrying a current $\mathrm{I}$ and placed in a uniform magnetic field $\mathrm{B}$. Indicate the direction of the torque on the loop.