Joint. The place where two or more conductors are united. Joint Resistance. The combined resistance offered by two or more substances or conductors. Jump Spark. A spark, disruptive in its character, between two conducting points. Initial Charge. The charge required to start a battery. Kathode, or Cathode. The negative plate or side of a battery. The plate on which the electro deposit is made. Key. The arm of a telegraph sounder. A bar with a finger piece, which is hinged and so arranged that it will make and break contacts in an electric circuit. Keyboard. A switch-board; a board on which is mounted a number of switches. Kilowatt. A unit, representing 1,000 watts. An electric current measure, usually expressed thus: K.W. Kilowatt Hour. The computation of work equal to the exertion of one kilowatt in one hour. Knife Switch. A bar of a blade-like form, adapted to move down between two fingers, and thus establish metallic connections. Laminated. Made up of thin plates of the same material, laid together, but not insulated from each other. Lamp Arc. A voltaic arc lamp, using carbon electrodes, with mechanism for feeding the electrodes regularly. Lamp, Incandescent. A lamp with a filament heated up to a glow by the action of an electric current. The filament is within a vacuum in a glass globe. Leak. Loss of electrical energy through a fault in wiring, or in using bare wires. Load. The ampere current delivered by a dynamo under certain conditions. Low Frequency. A current in which the vibrations are of few alternations per second. Magnet. A metallic substance which has power to attract iron and steel. Magnet Bar. A straight piece of metal. Magnet Coil. A coil of wire, insulated, surrounding a core of iron, to receive a current of electricity. Magnet Core. A bar of iron adapted to receive a winding of wire. Magnet, Field. A magnet in a dynamo. A motor to produce electric energy. Magnet, Permanent. A short steel form, to hold magnetism for a long time. Magnetic Adherence. The adherence of particles to the poles of a magnet. Magnetic That quality of a metal which draws metals. Also Attraction and the pulling action of unlike poles for each Repulsion. other, and pushing away of like poles when brought together. Magnetic Force. The action exercised by a magnet of attracting or repelling.