Force between two current-carrying wires

Magnetism arises from the interactions between conductors when they carry an electric current. When two parallel wires carry currents, their magnetic fields interact, causing the wires to either attract or repel each other. The direction of the currents determines whether the wires will experience an attractive or repulsive force.

Magnetic field patterns around current-carrying wires

Current in the same direction

When the currents in the two wires are in the same direction, the magnetic field lines combine to form loops around both wires. This field pattern is similar to that of two bar magnets with opposite poles close together, which attract each other. The combined magnetic field is stronger between the wires and weaker outside them.

Current in opposite direction

A strong magnetic field, like a strong electrostatic field, represents a large amount of stored energy. This energy can be reduced when the wires move apart, allowing the field lines to separate as well. This situation is similar to bar magnets with like poles close together, which experience a repulsive force.