If currents in two parallel wires flow in opposite directions, the force between the wires will be

CONCEPT:

Magnetic field:

• The space or region around the current-carrying wire/moving electric charge or around the magnetic material in which force of magnetism can be experienced by other magnetic material is called as magnetic field/magnetic induction by that material/current.
• It is denoted by B.
• The magnetic force per unit length between two parallel wires is given by;

Where μ0 = permittivity of free space, I1 = current in a first wire, I2 = current in a second wire,d = distance between two wires, and l = length of current-carrying wire.

EXPLANATION:​ 

• The magnetic force per unit length between two parallel wires is given by;

• If the conductor carries the current in the same direction, then the force between them will be attractive.
• If the conductor carries the current in the opposite direction, then the force between them will be repulsive. Therefore option 2 is correct.