Magnet, Permanent.
A bar of steel charged with residual magnetism. Steel possesses high
coercive force in virtue of which when once magnetized it retains part
of the magnetization.
Permanent magnets are generally straight bars or U shaped; they are
termed bar magnets, magnetic needles, horseshoe magnets, machine magnets
and otherwise, according to their shape or uses.
Magnet Pole.
The part of a magnet showing strongest polarity; the part which attracts
iron the most powerfully, and acts as the starting point for lines of
force.
Magnet Poles, Secondary.
Magnet poles are often not situated at the ends. Owing to inequality of
the material or other causes they may occupy intermediate positions on
the magnet. Such poles are called secondary poles.
Magnet Pole, Unit.
A unit magnet pole is one which exerts unit force on another unit pole
placed at unit distance from it. Unit force is the dyne; unit distance
is one centimeter.
Magnet, Portative Power of.
The power of sustaining a weight by attraction of its armature possessed
by a magnet. In general terms the adherence of the armature of a magnet
to the pole varies with the square of the number of lines of force which
pass through the point of contact. Hence an increased adherence of the
armature to a horseshoe electro-magnet is sometimes obtained by
diminishing the area of contact of one pole which concentrates the lines
of force. Steel magnets were frequently made with rounded ends to
increase the portative power.
Magnet, Simple.
A magnet made of one piece of metal, or at least magnetized as such; the
reverse of a compound magnet, which is magnetized piece by piece and
then fastened together.
Magnet, Solenoidal.
A magnet which is so uniformly magnetized and is so long in proportion
to its other dimensions that it virtually establishes two magnetic
poles, one at either end. It is a long thin bar so magnetized that all
its molecules would, considered as magnets, be absolutely equal.
(Daniell.) It acts like a solenoid, except that it is longer in
proportion than the solenoid generally is constructed.
Magnet, Sucking.
A magnet coil with movable or loose axial bar of soft iron.
The whole is usually mounted vertically. When a strong enough current is
passed the bar is drawn up into the coil as if by suction, whence the
name.