11
Mutual inductance between two coils. This induces voltage the second coil and the basic principle of
the transformer action which described later this chapter. The two coils
in this case are said possess mutual inductance, shown Fig.
.
Iron core
Lines of
magnetic flux
FIGURE 10.
Whentwoseparatecoilsareplacedclosetogether,astheyareinatransformer,
a current one coil produces magnetic flux which links with the second
coil.Alternating current theory and electrical machines
205
When the switch opened the current stops flowing and, therefore, the
magnetic flux collapses. The effect is
known self-inductance, just inductance, and one property any
coil. The unit inductance the henry (symbol H), commemorate the
work the American physicist Joseph Henry (1797–1878), and circuit is
said possess inductance henry when emf volt induced
in the circuit current changing the rate ampere per second.11.
Fluorescent light fittings contain choke inductive coil series with the
tube and starter lamp. The starter lamp switches and off very quickly,
causing rapid current changes which induce large voltage across the tube
electrodes sufficient strike arc the tube.10
An inductive coil choke.
FIGURE 10. 10. The collapsing magnetic flux induces emf into
the coil and this voltage appears across the switch contacts
