388 STANDARD ELECTRICAL DICTIONARY.

Multiple Wire Method for Working Electro-magnets.

A method for suppressing sparking in working electro-magnets intermittently. The magnet core is wound with a number (from four to twenty) of separate layers of fine wire. A separate wire is taken for each layer and all are wound in the same direction, from one end to the other of the s.p.a.ce or bobbin without returning. The ends are then joined so as to bring all the wires in parallel. The effect of this is that as the coils vary in diameter the time constants of each is different from that of the others, the coefficient of self-induction being less, and the resistance being greater for the coils farthest from the central axis. Thus the extra currents run differently in the different coils, and only a comparatively small spark can be produced owing to the division of forces thus brought about.

Fig. 249. DIAGRAM ILl.u.s.tRATING MULTIPLE WIRE WORKING.

Multiplex Telegraphy.

Any system of telegraphy transmitting more than four messages simultaneously over a single wire. Properly it should apply to all transmitting more than one, but conventionally has the above restricted meaning, distinguishing it from duplex and quadruplex telegraphy.

Multiplying Power of a Shunt.

When a resistance is placed in parallel with a galvanometer on a circuit the following relation obtains. Let s and g equal the resistances of the shunt and galvanometer respectively, S and G the currents in amperes pa.s.sing through them, V the potential difference between their common terminals, and A the whole current in amperes. Then we have A = ( (s + g ) / s ) * G and ( (s + g ) / s ) is termed the multiplying power of the shunt, as it is the factor by which the current pa.s.sing through the galvanometer must be multiplied by to produce the total current.

Muscular Pile.

A species of voltaic battery, often termed Matteueci's pile, made up of alternate pieces of muscle cut longitudinally and transversely respectively. The different pieces represent the elements of a battery, and their difference of potential is naturally possessed by the pieces.

Myria.

A prefix; one million times. Thus myriavolt means one million volts.

[Transcriber's note: Contemporary usage is mega, as in megavolt.]

389 STANDARD ELECTRICAL DICTIONARY.

N.

(a) Symbol for north pole or north-seeking pole of a magnet.

(b) Symbol for the number of lines of force in a magnetic circuit.

Nairne's Electrical Machine.

The cylinder electrical machine, q.v.

Napierian Logarithms.

A series of logarithms the base of whose system is 2.72818. They are also called hyperbolic logarithms.

Nascent State.

An element just separating from a combination possesses at that time higher affinities than after separation, and can effect more powerful chemical changes.

It is sometimes attributed to a differential time of existence in the atomic modification, before the freed atoms have united to form molecules.

Natural Currents.

A term for earth currents. (See Current, Earth.)

Needle.

(a) A term applied to a bar magnet poised horizontally upon a vertical point, or suspended in a horizontal position by a filament. Thus the magnet in a mariner's compa.s.s, which may be a substantial bar magnet, is called a magnetic needle.

(b) An indicator in general shape like the hand of a clock. (Sec Annunciator, Needle- Telegraph, Needle.)

Needle of Oscillation.

The magnetic needle poised horizontally, and used for measuring the intensity of the earth's magnetic field, or of an artificial magnetic field, by the method of oscillations. The intensities of the field is inversely as the square of the number of oscillations performed in a given time.

Needle, Telegraphic.

The index in needle telegraphy (see Telegraph, Needle), whose motions indicate the characters it is desired to transmit.

Negative Charge.

One of the two kinds of electric charges. The other is the positive.

By the double fluid hypothesis this is a.s.sumed to be a charge of a particular kind of electricity--negative electricity.

By the single fluid hypothesis it is supposed to be caused by the absence of part of the normal electricity of a surface. The reverse is held by some theorists.

The subject is so purely theoretical that neither of the two hypotheses is accepted as final.

[Transcriber's note: Current is a wire is the motion of negative electrons. Current in a electrolyte is the motion of positive ions and negative ions. Current in a plasma is the motion of electrons and positive ions.]

390 STANDARD ELECTRICAL DICTIONARY.

Negative Electricity.

The kind of electricity with which a piece of amber is charged by friction with flannel; resinous electricity. (See Electrostatic Series.)

In a galvanic battery the surface of the zinc plate is charged with negative electricity.

According to the single fluid theory negative electrification consists in a deficiency of electricity.

[Transcriber's note: Negative electrification is an excess of electrons.]

Negative Element.

In a voltaic cell the plate not dissolved by the solution; the one which is positively charged; the copper, platinum, or carbon plate in the usual type of battery.

The current is a.s.sumed to flow from negative element to positive element (the zinc plate) through the wire or other external conductor.