electric machine, electrical machine

1. A machine for exciting electricity by means of friction. Its inventor was Otto von Guericke, of Magdeburg, who made one, consisting of a sulphur globe, about 1647, following it by the air-pump about 1650. Sulphur was next exchanged for resin, which in turn was superseded by a gla cylinder, Von Guericke's "rubber" to excite electricity had been simply his hand. Instead of the hand Winckler, in 1740, introduced cushions of horsehair stuffed with silk. Bose, about the same date, collected the electricity on an insulated cylinder of tin-plate. Ramsden, in 1760, replaced the gla cylinder by a circular gla -plate. The gla is rotated between the surfaces of the rubbers, and the electricity which is generated pa es to the conductors on each edge of the disc, thence to the prime conductor, and finally to a Leyden jar or other object, as may be desired. By friction with the gla , the gla becomes positively and the rubbers negatively electrified. The latter communicate with the ground by means of a chain, which carries off the negative electricity as soon as it is produced. In Nairne's machine there is a cylinder which is rubbed by only one cushion. Armstrong's is a hydro-electrical machine. [HYDRO-ELECTRICAL.] In Holtz's the electricity is not developed by friction, but is whatever their peculiar forms, as distinct one from the other, are based upon the discoveries of Faraday, and Henry contemporaneously in 1832, that if a closed wire or conducting ring is moved acro a magnetic space, a current of electricity is generated in the wire. A dynamo-electric generator is the best apparatus devised for the appli cation of this principle to the production of an electric-current. A magnetic space is provided between the poles of two or more powerful magnets, and coils of wire are caused to traverse this magnetic space in such a way as to excite a current in them. The stronger the magnetism of the space, the longer the wire and the quicker it is moved, the stronger will be the current excited. The aim of inventors, therefore, is to construct their machines with powerful magnets and coils of wire having many turns, and to rapidly rotate these coils through the magnetic "field" by mounting them on an axle mechanical motor. As each coil or driven by a steam-engine or other bobbin of wire pa es between the poles of the magnet, a transient current is generated in it; but as there are a number of bobbins rapidly following each other, each with its transient current, the joint effect of the whole is a practically continuous current. TER, ELECTROSCOPE.] electric-meter, s . [ELECTRO ME- electric-motor, s. A machine for driving other machines or vehicles. using the electric-current as the motive Practically, it is an electric dynamo having current sup- plied to it by another dynamo or a battery. [ELECTRO-MOTOR.] electric-main, s. The main conductor in any system of distributing electricity.