Coercive or Coercitive Force.
The property of steel or hard iron, in virtue of which it slowly takes
up or parts with magnetic force, is thus termed ("traditionally";
Daniell). It seems to have to do with the positions of the molecules, as
jarring a bar of steel facilitates its magnetization or accelerates its
parting, when not in a magnetic field, with its permanent or residual
magnetism. For this reason a permanent magnet should never be jarred,
and permitting the armature to be suddenly attracted and to strike
against it with a jar injures its attracting power.
Coercive force is defined also as the amount of negative magnetizing
force required to reduce remnant magnetism to zero.
By some authorities the term is entirely rejected, as the phenomenon
does not seem directly a manifestation of force.
Coil and Coil Plunger.
A device resembling the coil and plunge, q. v., except that for the
plunger of iron there is substituted a coil of wire of such diameter as
to enter the axial aperture of the other, and wound or excited in the
same or in the opposite sense, according to whether attraction or
repulsion is desired.
Coil and Plunger.
A coil provided with a core which is free to enter or leave the central
aperture. When the coil is excited, the core is drawn into it. Various
forms of this device have been used in arc lamp regulators.
Synonym--Sucking coil.
Fig. 95. COIL AND COIL PLUNGER OF MENGIES ARC LAMP.
Fig. 96. COIL AND PLUNGER EXPERIMENT.