Consider, in relation to electrodynamics, what is a dipole moment. Elementary charge carriers flowing along a straight section of a system of conductors form a direct current. Accordingly, there is a current charge of the indicated current (I * L, where I is the current value, L is the length of the section). In turn, Ampere’s law considers two parallel current charges as L tends to infinity. In a closed loop, its two halves have a current opposite in direction, forming a current dipole. A vortex field is created around each such dipole, which is characterized by its own current dipole charge, oriented perpendicular to the plane in which the circuit is located. It is called the dipole moment. But since we consider only the current component, then for the transition to electromagnetism the same term is called differently. Another name is magnetic dipole moment (Pm, sometimes just m).
It is one of the key characteristics of any substance. It is believed that the dipole moment arises due to currents (both in the microworld and in macro systems). In this case, the microworld is understood as an atom: charges (electrons) moving in circular orbits can be considered as an electric current. Since the substance consists of elementary particles, each of them also has its own moment. Please note that elementary particles need to be understood not only as molecules and atoms, but also as protons, neutrons, electrons and, possibly, even smaller components. From the point of view of quantum mechanics, their magnetic dipole moment is caused by their own mechanical rotation - spin. However, this assumption has recently been increasingly called into question in the light of the latest field theory of particles. For example, the existence of the so-called anomalous dipole is widely recognized, the value of which differs from the calculations of the equation in quantum theory. But from the field point of view, in which the magnetic field of any elementary particle is not generated by the spin rotation of charge carriers, but is one of the constant components of the electromagnetic field, the anomalous dipole is easily explained. The value is defined as a specific set of quantum numbers with the corrective component of the spin. Thus, the magnetic moment for a neutron depends on the electric current generating it and the energy of the changing electromagnetic field.
When calculating its values for the whole circuit, the method of integral addition of the dipole moments of the simplest current dipoles creating a closed circular circuit is used.
The dipole moment in electrodynamics is determined by the formula:
Pm = S * I * n,
where I is the value of the flowing current; S is the area of the closed loop (circular); n is a vector directed perpendicular to the plane in which the contour is located. Although the above formula does not show this, the value of Pm is also vectorial, the direction of which can be determined by the rule of a gimlet (right screw) known in classical electrical engineering: if the rotation of an imaginary screw is compared with the direction of the flowing current, then the movement of the screw body will coincide with the desired vector.
The electric field of a dipole differs from the field of a point charge, first of all, by the configuration of the field lines. Since, from the point of view of physics, such a dipole is a balanced system of two electric charges, whose modules are equal and the polarity is opposite (+ and -), the corresponding tension lines begin at one charge and end at another. In the case of only one point carrier, the lines diverge in all directions, like the light of a lamp.