Two thin, long, parallel wires, separated by a distance $'d'$ carry a current of $'i'$ $A$ in the same direction. They will
repel each other with a force of ${\mu _0}{i^2}/\left( {2\pi d} \right)$
attract each other with a force of ${\mu _0}{i^2}/\left( {2\pi d} \right)$
repel each other with a force $_0{i^2}/\left( {2\pi {d^2}} \right)$
attract each other with a force of ${\mu _0}{i^2}/\left( {2\pi {d^2}} \right)$
