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 There are two ways in which electricity can be used for heating: the arc method and the resistance method. The arc is, of course, a special case of electric resistance (the air or other gas between the electrodes being the resistant medium) but it always produces intense heat, while the resistance of a solid conductor can be adapted to producing any temperature desired. The arc method is therefore confined to the melting of metals, including iron, steel, brass, etc., and to welding. In using the resistance method, the electric current may be sent directly through the material to be heated, produced by induction in this material, or sent through a heating unit separate from the material to be heated. The last of these three processes is the most versatile and the most widely used.



Electric heating costs more, per unit of heat produced, than heating by the use of fuel, but it offers many striking advantages over the latter process, and it is also in many cases much cheaper in the long run on account of incidental economies realized in its use. Heating with fuel means combustion, and combustion means that a great amount of air must be heated, much of this heat escaping up the chimney; that undesirable fumes and soot are produced, and that exact regulation of temperature is difficult or impossible. Electric heating is not a combustion process; it requires no air; produces no soot or fuel gases, and can be regulated as perfectly and easily in ordinary industrial work as under the conditions of the electrical laboratory. One of the many incidental advantages of electric heat is that it can generally be used without raising the temperature of the air in workrooms, and thus it is not, like combustion heating, a source of discomfort to the workmen.

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