Heat, Electric.
This term has been given to the heat produced by the passage of a
current of electricity through a conductor. It is really electrically
produced heat, the above term being a misnomer.
The rise of temperature produced in a cylindrical conductor by a current
depends upon the diameter of the conductor and on the current. The
length of the wire has only the indirect connection that the current
will depend upon the resistance and consequently upon its length.
The quantity of heat produced in a conductor by a current is in
gram-degree C. units equal to the product of the current, by the
electro-motive force or potential difference maintained between the ends
of the wire, by .24.
The cube of the diameter of a wire for a given rise of temperature
produced in such conductor by a current is equal approximately to the
product of the square of the current, by the specific resistance (q. v.)
of the material of the conductor, by .000391, the whole divided by the
desired temperature in centigrade units.
Heat, Electrical Convection of.
A term applied to the phenomena included under the Thomson effect, q.
v., the unequal or differential heating effect produced by a current of
electricity in conductors whose different parts are maintained at
different temperatures.
Heater, Electric.
An apparatus for converting electrical energy into thermal energy.
An incandescent lamp represents the principle, and in the Edison meter
has been used as such to maintain the temperature of the solutions.
Heaters for warming water and other purposes have been constructed,
utilizing conductors heated by the passage of the current as a source of
heat. (See also Heating Magnet.)
Heating Error.
In voltmeters the error due to alteration of resistance of the coil by
heating. If too strong a current is sent through the instrument, the
coils become heated and their resistance increased. They then do not
pass as much current as they should for the potential difference to
which they may be exposed. Their readings then will be too low. One way
of avoiding the trouble is to have a key in circuit, and to pass only an
instantaneous or very brief current through the instrument and thus get
the reading before the coils have time to heat.
The heating error does not exist for ammeters, as they are constructed
to receive the entire current, and any heating "error" within their
range is allowed for in the dividing of the scale.
Heating Magnet.
An electro-magnet designed to be heated by Foucault currents induced in
its core by varying currents in the windings. It has been proposed as a
source of artificial heat, a species of electric heating apparatus for
warming water, or other purposes.