where L is scalar known as self-inductance and depends only on the magnetic
permittivity μ of the media and the geometric parameters ΠL that determine the
size and the shape of the contour:
(39) L = f (μ, ∏ L)
Self-inducted voltage VL appears every time in electric cable when there is
change of the current i and this self-inducted voltage opposes to the change of
the current:
(40) VL = — L ∙ dt
Maxwell’s equations
In order to summarize the presented basic principles of electromagnetism it is
useful to write down the Maxwell’s equations. Although these equations have
been worked out a century ago they present in concise form the whole
electrodynamics.
I. Integral form in the absence of magnetic or polarizable media
Gauss' law for electricity
(41)
<f∫ E ∙ ds = —
ε0
Gauss' law for magnetism
(42) <∫ B ∙ dS = 0
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