[Transcriber's note: Contemporary long distance power transmission lines use 115,000 to 1,200,000 volts. At higher voltages corona discharges (arcing) create unacceptable losses.]

241 STANDARD ELECTRICAL DICTIONARY.

Energy, Kinetic.

Energy due to matter being actually in motion. It is sometimes called actual energy. The energy varies directly with the ma.s.s and with the square of the velocity. It is represented in formula by .5 *M * (v^2).

Synonyms--Actual Energy--Energy of Motion--Dynamic Energy.

Energy, Mechanical.

The energy due to mechanical change or motion, virtually the same as molar energy. (See Energy, Molar.)

Energy, Molar.

The energy of ma.s.ses of matter due to movements of or positions of matter in ma.s.ses; such as the kinetic energy of a pound or of a ton in motion, or the potential energy of a pound at an elevation of one hundred feet.

Energy, Molecular.

The potential energy due to the relations of molecules and set free by their change in the way of combination. It is potential for the same reason that applies to atomic and chemical energy, of which latter it is often a form, although it is often physical energy. The potential energy stored up in vaporization is physical and molecular energy; the potential energy stored up in uncombined pota.s.sium oxide and water, or calcium oxide (quicklime) and water is molecular, and when either two substances are brought together kinetic, thermal or heat energy is set free, as in slaking lime for mortar.

Energy of an Electrified Body.

An electrified body implies the other two elements of a condenser. It is the seat of energy set free when discharged. (See Dielectric, Energy of.) The two oppositely charged bodies tend to approach. This tendency, together with the distances separating them, represents a potential energy.

Energy of Stress.

Potential energy due to stress, as the stretching of a spring. This is hardly a form of potential energy. A stressed spring is merely in a position to do work at the expense of its own thermal or kinetic energy because it is cooled in doing work. If it possessed true potential energy of stress it would not be so cooled.

Energy of Position.

Potential energy due to position, as the potential energy of a pound weight raised ten feet (ten foot lbs.). (See Energy, Potential.)

Energy, Physical.

The potential energy stored up in physical position or set free in physical change. Thus a vapor or gas absorbs energy in its vaporization, which is potential energy, and appears as heat energy when the vapor liquefies.

242 STANDARD ELECTRICAL DICTIONARY.

Energy, Potential, or Static Energy.

The capacity for doing work in a system due to advantage of position or other cause, such as the stress of a spring. A pound weight supported ten feet above a plane has ten foot lbs. of potential energy of position referred to that plane. A given weight of an elementary substance represents potential chemical energy, which will be liberated as actual energy in its combination with some other element for which it has an affinity. Thus a ton of coal represents a quant.i.ty of potential chemical energy which appears in the kinetic form of thermal energy when the coal is burning in a furnace. A charged Leyden jar represents a source of potential electric energy, which becomes kinetic heat energy as the same is discharged.

Energy, Thermal.

A form of kinetic molecular energy due to the molecular motion of bodies caused by heat.

Entropy.

Non-available energy. As energy may in some way or other be generally reduced to heat, it will be found that the equalizing of temperature, actual and potential, in a system, while it leaves the total energy unchanged, makes it all unavailable, because all work represents a fall in degree of energy or a fall in temperature. But in a system such as described no such fall could occur, therefore no work could be done. The universe is obviously tending in that direction. On the earth the exhaustion of coal is in the direction of degradation of its high potential energy, so that the entropy of the universe tends to zero.

(See Energy, Degradation of.)

[Transcriber's note: Entropy (disorder) INCREASES, while AVAILABLE ENERGY tends to zero.]

Entropy, Electric.

Clerk Maxwell thought it possible to recognize in the Peltier effect, q.

v., a change in entropy, a gain or loss according to whether the thermo-electric junction was heated or cooled. This is termed Electric Entropy. (See Energy, Degradation of.)

243 STANDARD ELECTRICAL DICTIONARY.

Fig. 165. EPINUS' CONDENSER,

Epinus' Condenser.

Two circular bra.s.s plates, A and B, are mounted on insulating supports, and arranged to be moved towards or away from each other as desired.

Between them is a plate of gla.s.s, C, or other dielectric. Pith b.a.l.l.s may be suspended back of each bra.s.s plate as shown. The apparatus is charged by connecting one plate to an electric machine and the other to the earth. The capacity of the plate connected to the machine is increased by bringing near to it the grounded plate, by virtue of the principle of bound charges. This apparatus is used to ill.u.s.trate the principles of the electric condenser. It was invented after the Leyden jar was invented.

Fig. 166. EPINUS' CONDENSER.

E. P. S.

Initials of Electrical Power Storage; applied to a type of secondary battery made by a company bearing that t.i.tle.

Fig. 167. CAM EQUALIZER.

244 STANDARD ELECTRICAL DICTIONARY.

Equalizer.

In electro-magnetic mechanism an arrangement for converting the pull of the electro-magnet varying in intensity greatly over its range of action, into a pull of sensibly equal strength throughout. The use of a rocking lever acting as a cam, with leverage varying as the armature approaches or recedes from the magnet core is one method of effecting the result. Such is shown in the cut. E is an electro-magnet, with armature a. A and B are the equalizer cams. The pull on the short end of the cam B is sensibly equal for its whole length.

Many other methods have been devised, involving different shapes of pole pieces, armatures or mechanical devices other than the one just shown.

Equipotential. adj.

Equal in potential; generally applied to surfaces. Thus every magnetic field is a.s.sumed to be made up of lines of force and intersecting those lines, surfaces, plane, or more or less curved in contour, can be determined, over all parts of each one of which the magnetic intensity will be identical. Each surface is the locus of equal intensity. The same type of surface can be constructed for any field of force, such as an electrostatic field, and is termed an equipotential surface.

Equipotential Surface, Electrostatic.

A surface in an electrostatic field of force, which is the locus of all points of a given potential in such field; a surface cutting all the lines of force at a point of identical potential. Lines of force are cut perpendicularly by an equipotential surface, or are normal thereto.