
64
But if you are keen enough to pursue the magnetic relationships
farther you may care to note, starting from the fact that μ = B/H,
that one can derive the first formula for inductance in Sec. 4.6:
Β ΦΙ
so T
=
7
=
L
With 'air-core' coils, even when all the turns are close together it is
not correct to assume that all the flux due to each turn links with the
whole lot; and the error is of course much greater if the turns are
widely distributed as in Fig. 4Ab. An even greater difficulty is that
the flux does not all follow a path of constant area A and equal
length /.
A general formula for inductance has nevertheless been given, to
bring ou ...