R
Radiant Energy. Energy existing in the luminiferous ether and exercised in wave transmission, creating light or sound. Radium possesses the highest form of radiant energy.
Radiate. To emit or send out in direct lines from a point or points, as radiating heat, light, or sound. The radiations are sent out in all directions from a central point, just as a stone thrown in a pond of still water will radiate waves or ripples from the central point.
Radiation. The travelling or motion of ether waves through space.
Radiator, Electric. A series of plates or wire-coils heated by current. They radiate heat and so warm the surrounding air.
Radiograph. A photographic picture taken by the X-ray process.
Receiver. In telephony or telegraphy, an instrument for receiving the message as distinguished from the instrument sending or transmitting the message.
The telephone piece held to the ear is the receiver.
Receiving End. The end of a line where the operative currents are received, as opposed to the end at which they are transmitted.
Receptacle. A device for the installation of an attachment or extension plug. Used in connection with electric-lighting circuits.
Recoil Kick. Reaction resulting from a disruptive discharge.
Recorder. In telegraphy, the receiving apparatus for recording the dot-and-dash signals on a strip or tape of paper.
Reduction. The influence exerted without apparent communication by a magnetic field or a charged mass upon neighboring bodies. The induction-coil is a simple example of this force. The current passes through the primary or inner coil about a core of soft iron, and in doing so it develops lines of force in the secondary or outer coils, although no current is flowing directly through them from a battery or dynamo.
Reduction Gear. A gear which acts to reduce a speed below that of a motor in full motion without lessening its motive force.
Refract. To break the natural course of light in an elastic medium. The rays of light, as they pass from a rare into a dense medium, are refracted.
Register, Electric. An apparatus for registering and recording the movements of employés about a building. Press-buttons are arranged throughout the building, and when a man passes a station he presses the button, and the time is recorded by the apparatus.
Regulator Magnet. (See [Magnet, Regulator].)
Relay. A telegraphic or telephonic receiving instrument which opens and closes a local circuit through movements caused by the impulses of currents received. The relay battery may be very delicate so as to work with weak currents. The function of the relay is to open and close circuits for the admission of a new current to push on the sound or vibration to a more distant point. The main battery may be of any desired power.
Relay Connection. A connection used in telegraphy, including a local battery, with a short circuit, normally open, but closed at will by a switch and sounder, or other appliance. A very weak current will work the apparatus.
Relay, Ordinary. A relay that is not polarized.
Relay, Repeating. In telegraphy, a relay for repeating the signals through a second line.
Reluctance. Magnetic resistance.
Repeater. In telegraphy, an instrument for repeating the signals through a second line. It is virtually a relay which is controlled by the sender, and which, in turn, operates the rest of the main line. It is usually located at about the middle of the total distance covered.
Repeating-station. A telegraph station located on a long line, and occupying a position at the juncture of the sections into which the line is divided. The currents received through one section are repeated into the other sections by means of a repeater.
Repulsion, Electric. The tendency which exists between two bodies charged alike to mutually repel each other.
Residual Charge. (See [Charge, Residual].)
Resilience. The power to spring back to a former position. Electricity is resilient, although its elasticity cannot be measured accurately.
Resin. A solid inflammable substance or gum, and a good non-conductor in electrical work. It is the product obtained by distilling the sap of the pitch-pine. The name is also applied to the product of distilling the sap of other trees. Common resin, shellac, lac, Dragon’s-blood, and other substances of a similar nature are resins. They are all dielectrics, and the source of negative frictional electricity when rubbed with cotton, wool, flannel, silk, or fur.
Resistance. That quality of an electric conductor in virtue of which it opposes the passage of an electric current, causing the disappearance or modification of electro-motive force, and converting electric energy into heat energy.
Resistance-box. A box filled with resistance-coils connected in series and provided with a switch, so that any number of the coils may be cut out.
Resistance, Carbon. A resistance composed of carbon as a substitute for a coil of wire. Carbon rods are placed close together having an air space between them, with alternate ends connected. Piles may be built up of carbon plates, whose resistance is made to vary by changing the pressure.
Resistance-coil. A coil of wire metal or other substances having the power to resist a current of electricity.
A coil of wire used to measure an unknown resistance by virtue of its own known resistance. (See also [Coil, Resistance].)
Resistance, Dielectric. (See [Dielectric Resistance].)
Resistance, Electrolytic. The resistance of an electrolyte to the passage of a current decomposing it. It is almost entirely due to electrolysis, and is intensified by counter-electro-motive force. When a current of a voltage so low as not to decompose an electrolyte is passed through the latter, the resistance appears very high and sometimes almost infinite. If the voltage is increased until the electrolyte is decomposed the resistance suddenly drops to a point lower than the true resistance.
Resistance, Internal. The resistance of a battery, or generator, in an electric circuit as distinguished from the resistance of the rest of the circuit.
Resistance, Liquid. A liquid of varying specific gravity used to create resistance to the passage of the electric current.
Resistance effected by the use of liquid through which a current must pass to complete a circuit.
Resistance, Metallic. The resistance of metals to the electric current.
German-silver resistance as distinguished from that of water, carbon, or other substances.
Resistance, Ohmic. True resistance measured in ohms as distinguished from counter electro-motive force. (See also [Ohmic Resistance].)
Resistance, Spurious. The counter-electro-motive force. In its effect of opposing a current and in resisting its formation it differs from true resistance. True resistance diminishes current strength, absorbs energy, and develops heat. Spurious resistance opposes and diminishes a current without absorption of energy or production of heat.
Resistance, Standard. A known resistance employed to determine unknown resistances by comparison.
Resistance, True. The true resistance measured in ohms as distinguished from counter-electro-motive force.
Resonator, Electric. A small, open electric circuit with ends nearly touching. When exposed to electric resonance, or to a sympathetic electric oscillating discharge, a spark passes across the gap. The spark is due to inductance in the resonator.
Retentiveness. That property which enables steel to retain its magnetism.
Return. A line or conductor which carries current back to its starting-point after it has traversed a circuit. The best definition of a return is a circuit on which no new apparatus is installed.
Return-circuit. (See [Circuit, Return].)
Return-circuit, Railway. A grounded circuit used in trolley systems for ground returns through the tracks, they being joined by links or flexible wires so as to form perfect conductors. It is the negative side of the system, the positive being in the overhead or underground feed-wire or rail.
Reversibility. The principle by which any form of generator for producing a given form of energy may be reversed to absorb energy. The dynamo of the reversible type driven to generate current may be reversed and will develop power if a current is run through it.
Rheostat. An adjustable resistance. An apparatus for changing the resistance, without opening the circuit, by throwing a switch-bar across contact points.
Rod Clamp. A clamp used in the lamp rod of an arc-light to hold the carbon.
Röntgen Effects. Phenomena obtained by the use of the X or Röntgen rays.
Röntgen-ray Screen. A screen whose surface is covered with fluorescent material for the purpose of receiving and displaying the Röntgen image.
Röntgen Rays. A peculiar form of light radiation discovered by Röntgen, and which is emitted from that portion of a high vacuum tube upon which the kathode rays fall.
Rotary Magnetic Field. (See [Magnetic Field, Rotary].)
Ruhmkorff Coil. (See [Coil, Ruhmkorff].)