Fig. 5 Direction ofthe lines of the magnetic induction around axis with current (a)
and along the axis of contour with current (b). The current i by convention
denotes the flux ofpositive charges.
The united electromagnetic field manifests itself with resultant electromagnetic
force FR defined by the Coulomb-Lorentz formula:
(29)
—— —— ——
FR=q(E+vi×B)
where ι/i is the velocity of the charge q.
(30)
——
vi
dl dq ■ dl i ■ dl
dt dt ■ dq dq
If we have magnetically isotropic media then we could define another vector
describing the magnetic field called magnetic intensity H that is:
——
(31)
Hi = B
μ
where μ is the magnetic permeability of the media. The magnetic permeability of
the vacuum is denoted with μ0 ≈ 4π × 10-7 H/m.
24