Three { Magnetic, electromagnet, uses and applications. Principal { Chemical, electrolysis, applications. Effects: { Heat, lighting and heating devices. Theories: (a) of voltaic cells, (b) of electrolysis. Units: Ampere, ohm, volt, watt, joule, kilowatt, horse power. Measurement--(a) magnetic effect; galvanometer, ammeter, voltmeter, wattmeter, Wheatstone bridge, construction and use. (b) chemical effect; voltameter. Laws: (a) Right hand rules, for conductor and helix. (b) Resistance, Conductors in series and parallel. (c) Ohm's law, heat law, power law, 3 forms for each. (d) Cells in parallel and series. Problems: Upon applications of the laws and formulas studied. Devices. { Voltaic cells; wet, dry, and Daniell. and { Electrolysis and the storage battery. Instruments: { Measuring instruments, electric bell, sounder, { heating and lighting devices. Terms: Anode, cathode, electrolyte, ion, circuit switch, current, e.m.f., resistance, potential. CHAPTER XIV INDUCED CURRENTS (1) ELECTROMAGNETIC INDUCTION =296. Current Induced by a Magnet.=--The discovery in 1819 that a current in a conductor can deflect a magnetic needle or that it has a magnetic effect, led to many attempts _to produce an electric current by means of a magnet_. It was not until about 1831, however, that _Joseph Henry_ in America and _Michael Faraday_ in England, independently discovered how to accomplish this important result. At the present time, voltaic cells produce but a very small part of the current electricity used. Practically all that is employed for _power, light, heat, and electrolysis is produced by the use of magnetic fields, or by electromagnetic induction_. =297. Laws of Induced Currents.=[M]--To illustrate how a current can be produced by electromagnetic induction: [M] An induced current is one produced by changing the number of magnetic lines of force passing through a coil. Connect a coil of 400 or more turns of No. 22 insulated copper wire to a sensitive galvanometer. (See Fig. 279.) Now insert a bar magnet in the coil. A sudden movement of the galvanometer will be noticed, indicating the _production of a current_. When the magnet stops moving, however, the current stops, and the coil of the galvanometer returns to its first position. If now the magnet is removed, a movement of the galvanometer coil _in the opposite direction is_ noticed. This action may be repeated as often as desired with similar results.