Soldering, Electric.
(a) Soldering in which the solder is melted by means of electricity;
either current incandescence or the voltaic arc may be used. It is
identical in general with electric welding. (See Welding, Electric.)
(b) The deposition by electric plating of a metal over the ends of two
conductors held in contact. This secures them as if by soldering. It is
used in connecting the carbon filament of an incandescent lamp with the
platinum wires that pass through the glass. Copper is the metal usually
deposited.
Solenoid.
The ideal solenoid is a system of circular currents of uniform
direction, equal, parallel, of equal diameter of circle, and with their
centers lying on the same straight line, which line is perpendicular to
their planes.
Fig. 305. EXPERIMENTAL SOLENOID.
The simple solenoid as constructed of wire, is a helical coil, of
uniform diameter, so as to represent a cylinder. After completing the
coil one end of the wire is bent back and carried through the centre of
the coil, bringing thus both ends out at the same end. The object of
doing this is to cause this straight return member to neutralize the
longitudinal component of the helical turns. This it does approximately
so as to cause the solenoid for its practical action to correspond with
the ideal solenoid.
Instead of carrying one end of the wire through the centre of the coil
as just described, both ends may be bent back and brought together at
the centre.
A solenoid should always have this neutralization of the longitudinal
component of the helices provided for; otherwise it is not a true
solenoid.
Solenoids are used in experiments to represent magnets and to study and
illustrate their laws. When a current goes through them they acquire
polarity, attract iron, develop lines of force and act in general like
magnets.
A solenoid is also defined as a coil of insulated wire whose length is
not small as compared with its diameter.