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54 ELECTRIC DISCHARGES, WAVES AND IMPULSES.
or, substituting

gives equation (1).

/» 1 1

For X = 0 in equation (1), ™ = - ; for 3C = oo , <fc « - ; that is,

ov, a <r

in equation (1), - = initial permeability, - *» saturation value of

magnetic density.

If the magnetic circuit contains an air gap, the reluctance of the
iron part is given by equation (2), that of the air part is constant,
and the total reluctance thus is

where B = a plus the reluctance of the air gap. Equation (1),
therefore, remains applicable, except that the value of a is in-
creased.
In addition to the metallic flux given by equation (1), a greater

or smaller part of the flux always passes through the air or through
space in general, and then has constant permeance, that is, is given
by

(B » CX.

23. In general, the flux in an ironclad magnetic circuit can,
therefore, be represented as function of the current by an expression
of the form

where _— . = §' ig that part of the flux which passes through

Ji ~Y" Ot»

the iron and whatever air space may be in series with the iron,
and, d is the part of the flux passing through nonmagnetic
material.
Denoting now

Ji-nalO-,)

L₂ = nelO~⁸,$ ^w

where n = number of turns of the electric circuit, which is inter-
linked with the magnetic circuit, I/₂ is the inductance of the air
part of the magnetic circuit, L\ the (virtual) initial inductance, that
is, inductance at very small currents, of the iron part of the mag-



	54 ELECTRIC DISCHARGES, WAVES AND IMPULSES. or, substituting

	gives equation (1). /» 1 1 For X = 0 in equation (1), ™ = - ; for 3C = oo , <fc « - ; that is, ov, a <r in equation (1), - = initial permeability, - *» saturation value of magnetic density. If the magnetic circuit contains an air gap, the reluctance of the iron part is given by equation (2), that of the air part is constant, and the total reluctance thus is

	where B = a plus the reluctance of the air gap. Equation (1), therefore, remains applicable, except that the value of a is in- creased. In addition to the metallic flux given by equation (1), a greater or smaller part of the flux always passes through the air or through space in general, and then has constant permeance, that is, is given by (B » CX. 23. In general, the flux in an ironclad magnetic circuit can, therefore, be represented as function of the current by an expression of the form

	where _— . = §' ig that part of the flux which passes through Ji ~Y" Ot» the iron and whatever air space may be in series with the iron, and, d is the part of the flux passing through nonmagnetic material. Denoting now Ji-nalO-,) L₂ = nelO~⁸,$ ^w where n = number of turns of the electric circuit, which is inter- linked with the magnetic circuit, I/₂ is the inductance of the air part of the magnetic circuit, L\ the (virtual) initial inductance, that is, inductance at very small currents, of the iron part of the mag-