Derive an expression for the force between two long parallel current-carrying conductors.

A long straight wire $AB$ carries a current $I$. A proton $P$ travels with a speed $v$, parallel to the wire, at a distance $d$ from it in a direction opposite to the current as shown in Figure. What is the force experienced by the proton and what is its direction?

A rectangular current carrying loop $EFGH$ is kept in a uniform magnetic field, as shown in Figure.

What is the direction of the magnetic moment of the current loop?

A rectangular current carrying loop $EFGH$ is kept in a uniform magnetic field, as shown in Figure.

When is the torque acting on the loop $\left(A\right)$ maximum, $\left(B\right)$ zero?