The Standard Electrical Dictionary Part 107

The whole is usually mounted vertically. When a strong enough current is pa.s.sed the bar is drawn up into the coil as if by suction, whence the name.

367 STANDARD ELECTRICAL DICTIONARY.

Magnet, Unipolar.

No such thing as a unipolar magnet is possible. The name is given to poised or suspended magnets, one of whose poles lies in the axis of suspension. It is obvious that such a magnet will act, as far as its directive tendency and rotatory movements are concerned, as if it had only one pole. As shown in the cut, the pole s in both magnets lies in the axis of suspension or directly under the filament by which they are suspended, while the other pole n is the active pole in causing rotation or directive tendency; c c are counterweights or counterpoises.

Fig. 236. UNIPOLAR MAGNETS.

Magnetophone.

An apparatus for producing a loud sound, involving the principles of the telephone. A rapidly alternating or make and break current being produced by any means and being transmitted through the telephone gives a loud note of pitch dependent on the current producing it. Sometimes a perforated metallic disc is rotated in a magnetic field, and produces the requisite type of current.

Magnus' Law.

A law of thermo-electricity. In a h.o.m.ogeneous circuit, however, the temperature varies from point to point; there is no current.

Whatever potential differences may be established by the variations in temperature it is evident that they must counteract each other and reduce to zero.

Mains, Electric.

The larger conductors in a system of electric light or power distribution.

Make. v.

To complete a circuit, as by closing a switch.

Make and Break Current.

A current which is continually broken or interrupted and started again.

It is applied only where the "makes" and "breaks" succeed each other with great rapidity, as in the action of an induction coil or pole changer, etc. It has had considerable importance in litigation affecting the Bell telephone patents, the courts holding that the original Bell patent (No. 174,465, of 1876,) covered the undulating current, for the transmission of speech. Many efforts have been made by litigants to prove that specific telephones have transmitted articulate speech by the make and break current, but without success. If this could have been proved the a.s.sumption is that the courts would have sustained the use of such device as not infringing upon the claims of the Bell patent.

Malapterurus.

A fish, sometimes called the thunder fish, an inhabitant of African rivers, occurring in the Nile and Senegal. It possesses considerable electric power, similar to that of the gymnotus and torpedo, although inferior in amount.

368 STANDARD ELECTRICAL DICTIONARY.

Fig. 237. MALAPTERURUS.

Man-hole.

The cistern-like depression in the ground for giving access to the ends of tubes in electric conduits. (See Conduit, Electric Subway.)

Marked End or Pole.

The north pole or north seeking pole of a magnet, so called because it is usually marked with a notch or scratch by the maker. The south pole is called the unmarked end.

Ma.s.s.

The quant.i.ty of matter in a body. The C. G. S. unit of ma.s.s is the quant.i.ty of matter in a gram. While weight varies with lat.i.tude and other circ.u.mstances, ma.s.s is invariable.

The unit of ma.s.s is also defined as the quant.i.ty of matter which in a balance will counterpoise a standard ma.s.s, the gram or pound. As the gram is intended to be the ma.s.s of one cubic centimeter of water at 3.09? C. (39? F.), the C. G. S. unit of ma.s.s is really 1.000013 gram.

As a primary unit its dimensions are indicated by M.

Ma.s.s, Electric.

A term for quant.i.ty of electricity. The unit ma.s.s is such a quant.i.ty as at unit distance will act with unit force.

Matter, Electric.

The imaginary substance const.i.tuting electricity; a conception used purely as a matter of convenience.

[Transcriber's note: The electron was discovered five years after this publication.]

Matter, Radiant.

Matter in the ultra-gaseous or so-called fourth state. In the gaseous state the molecules of a gas are in perpetual kinetic motion, colliding actually or virtually with each other, rebounding from such approach, and striking also the walls of the containing vessel. But except for these deflections, which are of enormous frequency, the paths of the molecules would be perfectly straight.

In the radiant state matter exists in so high a vacuum that collisions of the molecules rarely occur, and the molecules simply beat back and forth in straight lines from side to side of the containing vessel.

A layer of gas in this condition is termed a Crookes' layer, from Prof.

William Crookes, who discovered and investigated these phenomena.

369 STANDARD ELECTRICAL DICTIONARY.

Luminous streams of the molecules are produced by electric high potential discharges between electrodes. The course of the discharge is normal, in general terms, to the surfaces of the electrodes, and reaches from one to the other in a curve or straight line, as the case may be.

These luminous streams are deflected by a magnetic field; if brought to a focus can heat refractory material in that focus to a full white heat, and can develop phosph.o.r.escence. The latter is termed electric phosph.o.r.escence. A great variety of experiments have been devised to ill.u.s.trate the phenomena of radiant matter. The vacuum is generally produced in a hermetically sealed gla.s.s vessel into which the electrodes are sealed, and which contain the phosph.o.r.escent substances or other essentials for the experiments. The vessels are termed Crookes' Tubes.

[Transcriber's note: Crookes reported on "radiant matter" in 1879. It is actually electrons, but he failed to distinguish them from ordinary atoms. Thompson properly described electrons in 1897.]

Matteueci's Experiment.

An experiment for showing the inductive effect of the discharge of a Leyden jar. Two gla.s.s plates are supported on standards in a vertical position. Flat coils of wire are wound or coiled and secured to one surface of each plate. One plate has much finer and longer wire than the other. Metal handles are connected to the ends of the coa.r.s.er wire coil.

The plates are placed with their coils facing each other. A Leyden jar is discharged through the coa.r.s.er coil, while the handles are grasped by a person. The shock of the discharge is felt by him.

Matting, Electric Floor.

Matting or floor covering underlaid with burglar alarm contacts, so arranged as to be closed by anyone walking on the matting. The contacts are connected to a burglar alarm system. The object is to provide an alarm if a burglar enters a house, in case he should enter a door or window without sounding the bell. The latter can be done by cutting out the window or part of the door instead of opening it.