ELECTRICITY is a form of energy (q.v.), like mechanical energy or energy of motion, heat, radiant energy (as light), chemical energy, etc. Electric energy is the form of energy most recently introduced into everyday life and is, therefore, not yet quite familiar, so that we still ask, °What is electricity?" while ages ago man kind ceased to ask, "What is gravity?" or °What is light?" although the manifestations of electric energy are no more wonderful and in explainable than those of gravity. That is, the cause why a stone falls to the ground and water flows down hill is just as mysterious as the manifestations of electricity. In nature electric energy manifests itself during atmospheric dis turbances as lightning (q.v.), but the energy of lightning is too erratic for use. For the pro duction of electric energy on a larger scale re course must be had to the stores of energy afforded by nature. In large amounts energy is found in nature, first, as mechanical energy in the waterfalls and to a lesser extent the wind, and second, as chemical energy in coal, wood, oil, natural gas, etc.
Generation,— In the transformation of the mechanical energy of waterfalls into electric energy, the water power is first converted into rotary motion by the turbine or water-wheel, the latter then converted into electric energy by the electric generator or dynamo. Chemical en ergy can be converted directly into electric energy only to a limited extent, as chemical energy of metals. This is done in the electric battery. (See ELECTRIC BATTERY). But due to the high cost of the chemical energy of metals, the production of electric energy by means of the battery is commercially feasible only where small quantities are required and the cost of the energy therefore secondary to the convenience of generation, as for signaling purposes, bells, annunciators, etc. The chemical energy of coal and other combustibles cannot be directly con verted into electric energy, but is converted into heat energy by combustion, the heat energy transferred from the gases of combustion to the water in the steam boiler, converted into me chanical energy in the steam engine or steam turbine and the mechanical converted into elec tric energy in the electric generator. In the gas engine the heat energy of combustion is directly converted into mechanical energy. In
any transformation of energy from one form to another a certain loss occurs by conversion into heat. This loss is moderate in the transforma tion of water power into mechanical energy, very small in the transformation of mechanical into electric energy, but enormous in the trans formation of heat into any other form of energy. Our modern theories consider all forms of energy as different modes of motion; of the masses in mechanical energy, or of the molecules and atoms of matter or of the elec trons with electric, chemical, etc., energy. Heat is the simplest form of energy, irregular motion of the molecules or motion without definite speed and direction. It is, therefore, intelligible that in any conversion of energy, that is, of a regular motion into another regular motion, some of the energy is lost by losing its regu larity of motion, that is, converted into heat, the more the greater the difference between the two forms of motion, and that when convert ing irregular into regular motion, that is, heat into other forms of energy, this loss is specially great. The cost of electric power derived from water power does not differ much from that derived from coal by the steam engine, the cost of coal in the latter case offsetting the interest on the greater investment required in developing the water power and transmitting the electric power to the place of consumption. Hence where coal is cheap the steam power may be more economical, and where water power is found which can cheaply be developed, or where coal is expensive, water power is more economical.
Use.— Electric energy is hardly ever used as such, but only after transformation into other forms of energy, mainly mechanical energy, heat, chemical energy and light. Since electric en ergy is generated from other forms of energy, it follows that it is used essentially as an inter mediary form of energy. For this it is better suited than any other form of energy, due to the high efficiency and simplicity of generation and reconversion and especially the almost unlim ited flexibility which permits transmission over long distance, distribution with the simplest means and unlimited subdivision and ease of control.