Siła magnetyczna między dwoma równoległymi prądami

Consider two infinitely long, parallel conductors carrying current in the same direction.

The force exerted by the magnetic field due to the first conductor, over a finite length of the second conductor, is given by the current multiplied by the vector product of the length vector and the field due to the first conductor.

The magnetic field is perpendicular to the length vector. Substituting the expression for magnetic field, the magnitude of the force on the second conductor is obtained.

According to the right-hand rule for the cross-product, the force on the second conductor points toward the first conductor.

Similarly, it can be shown that the field due to the second conductor exerts an equal magnitude of the force on the first conductor. However, the direction of this force is toward the second conductor.

Thus, for current flowing in the same direction, the magnetic field created around each conductor exerts an attractive force on the other.

If the current direction is reversed in either one of the conductors, there would be a repulsive force between the conductors.