The first transformer. It was made by Michael Faraday. It was a ring of soft iron 7/8 inch thick, and 6 inches in external diameter. It was wound with bare wire, calico being used to prevent contact of the wire with the ring and of the layers of wire with each other, while twine was [...]

An apparatus for showing that the electric charge resides on the surface. It consists of a net, conical in shape and rather deep, to whose apex two threads, one on each side, are attached. Its mouth is fastened to a vertical ring and the whole is mounted on an insulating support. It is pulled out [...]

A disc of any metal, mounted so as to be susceptible of rotation in a magnetic field of force, with its axis parallel to the general direction of the lines of force. A spring bears against its periphery and another spring against its axle. When rotated, if the springs are connected by a conductor, a [...]

A non-luminous space between the negative and positive glows, produced in an incompletely exhausted tube through which a static discharge, as from an induction coil, is produced. It is perceptible in a rarefaction of 6 millimeters (.24 inch) and upwards. If the exhaustion is very high a dark space appears between the negative electrode and [...]

To determine the surface action of a charge, Faraday constructed a room, twelve feet cube, insulated, and lined with tinfoil. This room he charged to a high potential, but within it he could detect no excitement whatever. The reason was because the electricity induced in the bodies within the room was exactly equal to the [...]

The effect of rotation of its plane produced upon a polarized beam of light by passage through a magnetic field. (See Magnetic Rotary Polarization.)

The practical unit of electric capacity; the capacity of a conductor which can retain one coulomb of electricity at a potential of one volt. The quantity of electricity charged upon a conducting surface raises its potential; therefore a conductor of one farad capacity can hold two coulombs at two volts potential, and three coulombs at [...]

A thermometer scale in use in the United States and England. On this scale the temperature of melting ice is 32°; that of condensing steam is 212°; the degrees are all of equal length. Its use is indicated by the letter F., as 180° F. To convert its readings into centigrade, subtract 32 and multiply [...]

Abbreviation for Fahrenheit, as 10º F., meaning 10º Fahrenheit. (See Fahrenheit Scale.)