Points of Derivation.
The point where a single conductor branches into two or more conductors,
operating or acting in parallel with each other.
Polar Angle.
The angle subtended by one of the faces of the pole pieces of the field-
magnet of a dynamo or motor. The centre of the circle of the angle lies
in the axis of the armature.
Synonym--Angle of Polar Span.
Polar Extension.
An addition made of iron to the poles of magnets. Various forms have
been experimented with. The pole pieces of dynamo field magnets are
polar extensions.
Synonyms--Pole Piece--Polar Tips.
Polarity, Diamagnetic.
The induced polarity of diamagnetic substances; it is the reverse of
paramagnetic polarity, or of the polarity of iron. A bar of diamagnetic
material held parallel with the lines of force in a magnetic field has a
like pole induced in the end nearest a given pole of the field magnet,
and vice versa. This theory accounts for the repulsion by a magnet of a
diamagnetic substance. The existence of this polarity is rather an
assumption. It originated with Faraday.
Polarity, Paramagnetic.
The induced polarity of paramagnetic substances, such as iron, nickel,
or cobalt.
When such a substance is brought into a magnetic field the part nearest
a specific pole of a magnet acquires polarity opposite to that of such
pole and is thereby attracted.
Another way of expressing it, in which the existence of a pole in or
near to the field is not implied, is founded on the conventional
direction of lines of force. Where these enter the substance a south
pole is formed and where they emerge a north pole is formed.
Such polarity tends always to be established in the direction of
greatest length, if the body is free to rotate.