Ampere-turns.

The amperes of current supplied to a magnet coil multiplied by the number of turns the current makes in the coil. If the coil is wound two or three in parallel, the virtual turns by which the amperes are multiplied are one-half or one-third the actual turns of wire.

Synonym--Ampere Windings.

Ampere-turns, Primary.

The ampere-turns in the primary coil of an induction coil or transformer.

Ampere-turns, Secondary.

The ampere-turns in the secondary coil of an induction coil or transformer.

Amplitude of Waves.

Waves are distinguished by length and amplitude. The latter, in the case of transverse waves, such as those of water and of the ether, correspond with and measure the height from lowest to highest point, or from valley to summit of the waves in question. In the case of longitudinal waves, such as those of the air, due to sounding bodies, the ratio of degree of rarefaction to degree of condensation existing in the system is the amplitude. The latter can be graphically represented by a sinuous line, such as would represent the section of a transverse wave. Ether waves are produced by heated bodies and by electro-magnetic impulses, as in the discharge of the Leyden jar.

The amplitude of a wave, other things being equal, is the measure of its intensity. Thus, the louder a sound the greater is the amplitude of the system of waves to which it is due. The same applies to ether waves, whether they are perceived in the electro-magnetic, light, or heat-giving modification. As the amplitude of ether waves cannot be accurately known, amplitude is a relative term and is not stated generally in any absolute unit.

a.n.a.logous Pole.

One of the elements of a pyro-electric crystalline substance, such as tourmaline. When heated, such bodies acquire electrical properties. If of such crystalline form that they are differently modified at the ends of their crystalline axis, by hemihedral modifications, the ends may be differently affected. One end may show positive electricity when the temperature is rising, and negative when falling. Such end is then called the a.n.a.logous pole. The opposite end presents, in such cases, the opposite phenomena; becoming negative when the temperature is rising, and becoming positive when it is falling; such end is called the antilogous pole.

a.n.a.lysis.

The determination of the elements of a case. It may be chemical, and consist in finding what a substance consists of; it may be mathematical, and consist in determining the unknown quant.i.ties in a problem; or it may belong to other branches of science. The term has a very extended application. Where the const.i.tuents are only determined in kind it is called qualitative a.n.a.lysis; where their quant.i.ty or percentage is ascertained it is called quant.i.tative a.n.a.lysis.

32 STANDARD ELECTRICAL DICTIONARY.

a.n.a.lysis, Electric.

Chemical a.n.a.lysis by electrolytic methods. (See Electrolytic a.n.a.lysis.)

a.n.a.lyzer, Electric.

An apparatus used in investigations on electric ether waves. It consists of a series of parallel metallic wires. When the electric waves have been polarized, the a.n.a.lyzer will only permit them to go through it intact, when the plane of vibration of the waves is parallel to its wires.

Anelectrics.

(a) Bodies which do not become electrified by friction; a term introduced by Gilbert, now little used, as all bodies develop electricity under proper conditions by contact action; the reverse of idioelectrtics.

(b) Also a conductor of electricity, the reverse of a dielectric, q. v.

(See Conductor.)

It will be seen that Gilbert's anelectrics were, after all, the same as the modern anelectrics, i.e., conductors.

Anelectrotonus.

A term used in medical electricity or electro-therapeutics to indicate the deceased functional activity induced in a nerve by the proximity of the anode of an active electric circuit completed through the nerve. The converse of Kathelectrotonus.

Angle of Declination.

The angle of error of the magnetic needle or compa.s.s, measuring the extent of its deviation from the meridian in any locality. It is the angle between the plane of the magnetic axis of a magnetic needle free to take its natural position, and the geographical meridian, the needle being counterpoised if necessary, so as to hold an absolutely horizontal position. The deviation is expressed as being east or west, referring always to the north pole. (See Magnetic Elements.)

Synonym--Variation of the Compa.s.s.

[Transcriber's note: See Agonic Line.]

Angle of the Polar Span.

In a dynamo or motor the angle subtended by the portion of a pole piece facing the armature, such angle being referred to the centre of the cross-section of the armature as its centre.

STANDARD ELECTRICAL DICTIONARY. 33

Angular Velocity.

The velocity of a body moving in a circular path, measured with reference to the angle it pa.s.ses over in one second multiplied by the radius and divided by the time. A unit angle is taken (57?.29578 = 57? 17' 44".8 nearly) such that it is subtended by a portion of the circ.u.mference equal in length to the radius. Hence, the circ.u.mference, which is 360?, is equal to 2*PI*unit angle, PI being equal to 3.1416--.

"Unit angular velocity" is such as would in a circle of radius = 1 represent a path = 1, traversed in unit time = 1 second. If the radius is r and the angle pa.s.sed over is theta, the distance is proportional to r*theta; if this distance is traversed in t seconds the angular velocity is theta / t. The angular velocity, if it is multiplied by r, theta expressing a distance, will give the linear velocity. The dimensions of angular velocity are an angle (= arc / radius) / a Time = (L/L)/T = (T^-1).

The velocity expressed by the rate of an arc of a circle of unit radius, which arc subtends an angle of 57? 17' 44".8, such arc being traversed in unit time, is unit angular velocity.

Animal Electricity.

Electricity, notably of high tension, generated in the animal system, in the Torpedo, Gymnotus and Silurus. The shocks given by these fish are sometimes very severe. The gymnotus, or electric eel, was elaborately investigated by Faraday. It has the power of voluntarily effecting this discharge. There is undoubtedly some electricity in all animals. The contact of the spinal column of a recently killed frog with the lumbar muscles produces contraction, showing electric excitement. Currents can be obtained from nerve and muscle, or from muscle sides and muscle cut transversely, in each case one thing representing positive and the other negative elements of a couple.

Angle of Inclination or Dip.

The angle which the magnetic axis of a magnet, which magnet is free to move in the vertical plane of the magnetic meridian, makes with a horizontal line intersecting such axis. To observe it a special instrument, the dipping compa.s.s, inclination compa.s.s, dipping needle, or dipping circle, as it is called, is used. (See Elements, Magnetic, --Dipping Needle,--Compa.s.s, Inclination.)

Angle of Lag.

The angle expressing the displacement of the magnetic axis of the armature core of a dynamo in the direction of its rotation. (See Lag.) Lag is due to the motion of the armature core.

Angle of Lead.

The angle expressing the displacement in the direction of rotation of the armature of a dynamo which has to be given the brushes to compensate for the lag. (See Lag.) This is positive lead. In a motor the brushes are set the other way, giving a negative angle of lead or angle of negative lead.

Anion.

The electro-negative element or radical of a molecule, such as oxygen, chlorine or the radical sulphion. (See Ions.) It is the portion which goes to the anode, q.v., in electrolytic decomposition.

34 STANDARD ELECTRICAL DICTIONARY.

Anisotropic. (adj.) Unequal in physical properties, as in conduction and specific inductive capacity, along various axes or directions. An anisotropic conductor is one whose conductivity varies according to the direction of the current, each axis of crystallization in a crystalline body marking a direction of different conductivity. An anisotropic medium is one varying in like manner with regard to its specific inductive capacity. In magnetism an anisotropic substance is one having different susceptibilities to magnetism in different directions. The term is applicable to other than electric or magnetic subjects.