INDUCTORS AND INDUCTANCE

PHY110W MAGNETISM INDUCTANCE
MUTUAL INDUCTION
To distinguish it from self-induction, the induction of an
emf in another nearby coil (caused by changing current
– and hence changing magnetic flux) in a coil is better
referred to as mutual induction.
The mutual inductance M 21 of coil 2 with respect to
coil 1 is given by
M
21
N
Φ
2 21
= (31-62)
i1
and hence the emf induced in coil 2 due to the
changing current in coil 1 is
di
=−M dt
1
E 2 21
(31-63)
Similarly,
di
=−M dt
2
E 1 12
(31-64)
where
M
12
=
N Φ
i
1 12
2
But actually M 12 = M 21 = M (31-65)
SI unit:
(as for self-induction)
the henry, H [1 H = 1 T.m 2 /A]
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