JEE MAIN - Physics (2005 - No. 49)
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 $${\mu _0}{i^2}/\left( {2\pi {d^2}} \right)$$
Giải thích
$${F \over \ell } = {{{\mu _0}{i_1}} \over {2\pi d}} = {{{\mu _0}{i^2}} \over {2\pi d}}$$
(attractive as current is in the same direction)
(attractive as current is in the same direction)