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Amperage
Charged particles carrying current in conductors, at the same time, in irregular thermal motion (with speed) and under the influence of field forces, in orderly motion (u- speed).
If the conductor is located in a magnetic field, the average value of the magnetic forces acting on each charged particle is:
(8.3)
The mean value of the random velocity vector is zero. Therefore, (1) is written as follows.
(8.4)
Figure 8.2.
The magnetic forces determined by (8.4) are transferred to the conductor through the collision of charged particles with the grid. If we define the number of charge carriers per unit volume of the conductor as n –, the force acting on the dl-element of the conductor can be expressed as follows (Fig. 8.2)
(8.5)
we write the current through its density:
(8.6)
From (8.5) and (8.6):
(8.7)
(8.7) is the force exerted by the magnetic field on the current conductor, which was determined by Ampere (1820) in direct experiment.
This is the modulus of the force
(8.8)
The direction of the ampere force is determined according to the left-hand rule. If the palm of the left hand is placed in such a way that the vector of magnetic induction enters, and all four fingers are placed in line with the direction of the current, then our thumb will show the direction of Ampere's force (Fig. 8.2, 8.3).
Putting the expression of the magnetic induction vector of a direct current conductor into (8.8), it is possible to derive the law of interaction of parallel currents.
(8.9)
(8.10)
The force acting on parallel current conductors per unit length is directly proportional to the current passing through each conductor, and inversely proportional to the distance between them (Fig. 8.4)
(8.11)
here:
Figure 8.4