P
Paper Cable. A cable insulated with waxed or paraffined paper.
Paraffine. A residuum of petroleum oil, valuable as an insulating medium in electrical work.
A hydro-carbon composition of the highest resistance known. It is extensively used in condensers and other electrical apparatus as a dielectric and insulator.
Parallel Distribution. A distributing system for electricity wherein the receptive contrivances are adjusted between every two of a number of parallel conductors running to the limits of the system. When two or more conductors connect two mains of comparatively large size and low resistance, they are said to be in parallel or in multiple. This order is easily pictured by imagining the mains to be the sides of a ladder and the conductors the rungs. In the latter the lamps are placed. It follows that the current flows from one main to the other through the conductors and lamps.
Paramagnetic. Substances which have magnetic properties, or those which are attracted by magnetic bodies. A paramagnetic substance has high multiplying power for lines of force, therefore a bar of iron which is a paramagnetic substance of the highest quality becomes magnetic when placed within a circle of electric lines of force. The first example of paramagnetic substance brought to the attention of man was the lodestone, from which the ancient mariners fashioned their crude compass needles.
P-C. An abbreviation for porous cup.
Pear Push. A push-button enclosed in a handle having the shape of a pear. It is generally attached to the end of a flexible wire cord.
Periodic Current. (See [Current, Periodic].)
Permanency, Electric. The power of conductors to retain their conductivity unaffected by the lapse of time.
Permanent Magnet. (See [Magnet, Permanent].)
Phase. One complete oscillation. The interval elapsing from the time a particle moves through the middle point of its course to the instant when the phase is to be stated.
Simple harmonic motion. Oscillation.
’Phone. An abbreviation for the word Telephone.
Phonograph. An apparatus for reproducing sound. It is vibratory and not electric in its action, except that the mechanism may be driven by electricity. It consists of a rotating cylinder of a waxlike material and a glass diaphragm carrying a needle-point that lightly touches the surface of the waxen cylinder. If the diaphragm is agitated the needle vibrates, making indentations in the surface of the wax. If the needle is set back and the cylinder rotated so as to carry the point over the indentations, the sound is given back through the vibration of the diaphragm.
Pickle. An acid solution used to cleanse metallic surfaces preparatory to electro-plating.
Pilot Wires. Wires brought from distant parts of electric light and power mains, and leading to voltmeters at a central station. Through their agency the potential energy of every part of the system may be measured.
Pith-balls. Balls made from the pith of light wood, such as elder. They are used in the construction of electroscopes and for other experiments in static electricity.
Plant. The apparatus for generating electric current, including engines, boilers, dynamos, mains, and subsidiary apparatus.
Plate, Condenser. In a static apparatus, the condenser having a flat piece of glass for a dielectric. It is mounted on an axle so that it may be revolved.
Plate, Ground. In a lightning-arrester, the plate connected to the earth or ground wire.
Plate, Negative. In a voltaic battery, the plate which is unattacked by the fluid. It is made of carbon, platinum, or copper.
Plate, Positive. (See [Positive Plate].)
Plating-bath. A vessel of solution for the deposition of metal by electrolysis. Used in electro-plating.
Plating, Electro. The process of depositing metal on surfaces of metals or other substances by the aid of an electrolyte and the electric current.
Platinum Fuse. A slender wire of platinum roused to incandescence by current, and used to explode a charge of powder or other combustible substance.
Plug. A piece of metal, with a handle, used to make electric connections by being inserted between two slightly separated plates or blocks of metal.
A wedge of metal, slightly tapered, and used to thrust between two conductors to close or complete a circuit.
Plumbago. Soft, lustrous graphite; a native form of carbon sometimes chemically purified. It is used chiefly in electrotyping for dusting the wax moulds to make the surface an electric conductor.
Plunge-battery. (See [Battery, Plunge].)
Polar. Pertaining to one of the poles of a magnet.
Polarity. The disposition in a body to place its axis in a particular direction when influenced by magnetism. For example, the attraction and repulsion at the opposite ends of a magnet. The N and S seeking poles of a compass needle is the simplest example.
Polarity, Electric. The disposition in a paramagnetic body to be influenced by electric waves and lines of force. The otherwise non-magnetic body or mass becomes magnetic to attract or repulse when influenced by electricity, but ceases to retain the phenomena after the electric influence is removed. A piece of soft iron wire, a nail, or a short rod of iron will become electro-polarized when a current of electricity is sent through a coil of insulated wire so wound that one end will be N the other S. So soon as the circuit is broken the polarity ceases.
Polarization. The depriving of a voltaic cell of its proper electro-motive force. This may be brought about through the solution becoming spent, or in the event of the acid being saturated with zinc, and so failing to act on the metallic zinc.
Counter electro-motive force due to the accumulation of hydrogen on the negative plate.
Polarizing-current. (See [Current, Polarizing].)
Polar Surface. The surface of a magnetic substance through which the magnetic flux passes in or out.
Pole-changer. An automatic, oscillating switch or contact-breaker which reverses the direction of the current.
Pole, Negative. The S pole in a magnet or compass needle.
Pole, Positive. (See [Positive Pole].)
Pole-switch, Single. A switch designed to open or close one lead only.
Poles. The terminals of an open electric circuit at which there necessarily exists a potential difference.
The terminals of an open magnetic circuit, or the ends of a magnetized mass of iron.
Porcelain. A fine variety of earthenware, valuable for insulators and insulating purposes.
Porosity. The state or property of having small interstices or holes. The opposite of density.
Porous Cup or Cell. A cup or cell made of pipe-clay or of unglazed earthenware through which a current of electricity can pass when wet or in a liquid. Porous cups are used in cells and batteries to keep two liquids apart, and yet permit electrolysis and electrolytic conduction.
Positive Currents. Currents which deflect the needle to the left.
Positive Electricity. The current that flows from the active element, the zinc in a battery, to the carbon. The negative electricity flows from the carbon to the zinc.
Positive Electrode. The electrode which is connected with the positive pole of a source of electric energy.
Positive Feeders. The lead or wire in a set of feeders which is connected to the positive terminal of the generator.
Positive Plate. In a voltaic cell, the plate which is acted upon and corroded. The current from the positive plate is negative electricity.
Positive Pole. The N pole in a magnet or magnetic needle. So called because it seeks the north or negative pole of the earth.
Positive Wire, or Conductor. The wire, or conductor, connected with the positive pole of any apparatus which produces electro-motive force.
Potential, Electric. The power to perform electric work.
Potential Energy. Capacity for doing work. Potential energy when liberated becomes actual energy for the performance of work.
Power-generator. Any source from which power is generated.
Power-house. A station in which the plant of an electric power system is operated and the current distributed to local or long-distance points. Power-houses are either primary or secondary stations. In the primary station the current is generated directly by the aid of mechanical power, either the steam-engine or the steam-turbine. The secondary station, or sub-station, is located at a distance from the main power-house, and has no mechanical means of generating current. The current, usually of high alternating voltage, is supplied to the sub-station from the main power-house; and by means of transformers and converters, the high-voltage current is transformed into one of lower E-M-F and higher amperage, for distribution over local lines.
Power-unit. The unit of electric power is the volt-ampere or watt.
Pressure, Electric. Electro-motive force or voltage.
Primary. A term used to designate the induction-coil in an induction-apparatus or transformer. It is an abbreviation for primary coil.
Primary Battery. (See [Battery, Primary].)
Prime Conductor. (See [Conductor, Prime].)
Push-button. A switch for closing a circuit by means of pressure applied to a button. The button is provided with a spring, so that when pushed in and released it flies back, reopening the circuit.
Pyrogravure. A process of engraving by the use of platinum points heated to redness by the electric current.