H = I^{2} R × t × .24 =Use of Heat from Electric Current.=--In the transmission of electricity from place to place, it is very desirable that none of the energy be expended in heating the conductor. Hence copper wires of the proper size must be used. In wiring a building for electric lights, the insurance rules require that the wires be of a certain size and that they be put up in a certain manner. Otherwise they will not insure a building against fire. It is often desirable, however, to use the electric current for the purpose of producing heat. The carbons of the arc and incandescent lamps are intensely heated that they may produce light. Coils of German silver wire or other high resistance wire are heated by the passage of a current through them. In this manner the electric stove is made. Soldering coppers, smoothing irons, and baking ovens are heated in a similar manner. =Magnetic Effect.=--An electric current flowing in a wire causes it to be surrounded by a _magnetic field_, which consists of _lines of force_ encircling the wire. The field is strongest near the wire and diminishes gradually in strength at increasing distances therefrom. The presence of this magnetic field is shown by various experiments and the subject is fully explained in chapter IX on _magnetism_. =Chemical Effect.=--Pats van Trostwyk (1789) pointed out that an electric discharge was capable of decomposing water; to show this he used gold wires, which he allowed to dip in water, connecting one of them with the inner, and another with the outer coating of a Leyden jar, and passing the discharge through the water. The gas bubbles collected proved to consist of oxygen and hydrogen gas. Nicholson and Carlisle (1800) dipped a copper wire which was connected with one of the poles of a voltaic pile into a drop of water, which happened to be on the plate connected with the other pole; gas bubbles appeared, and the drop of water became smaller and smaller. This experiment was repeated in a somewhat different manner, the brass wires from a pile being brought under a tube filled with water and closed at the top. Gas bubbles were produced by the wire in connection with the negative pole of the pile, and the water was observed to diminish gradually. At the positive wire, on the contrary, no gas came off, but the metal lost its metallic lustre, became dark, and finally crumbled away. The gas which had collected in the tube proved to be hydrogen; while on examining the black mass it was found that the constituents of brass, viz., copper and zinc, had become oxidized. [Illustration: FIG. 89.--An electrolytic cell. The parts are: A, cell; B, electrolyte; C, positive electrode or cathode; D, negative electrode or cathode.[9]] =Electrolysis.=--_Electric analysis_ or more briefly _electrolysis_ was the term applied by Faraday to the process of decomposing a liquid by the passage of a current of electricity through it.