Appendix Table I

ELECTRICAL TERMS

• AGONIC: An imaginary line of the earth's surface passing through points where the magnetic declination is 0°, that is, points where the compass points true north.
• ALTERNATOR: An alternating current generator. Ammeter: The instrument for the measurement of current.
• AMPERE: The unit of electrical current.
• AMPERE-HOUR: The quantity of electricity equivalent to a current of one ampere flowing past a point in a conductor in one hour.
• AMPERE-TURN: The magnetizing force produced by a current of one ampere flowing through a coil of one turn.
• ANODE: The electrode in a cell (voltaic or electrolytic) that attracts the negative ions and repels the positive; the positive pole.
• ARC: The luminous glow between incandescent electrodes.
• ARMATURE: The movable part of a motor or the removable part of a magnetic circuit, such as the iron placed across the poles of a horseshoe magnet.
• AUTO-TRANSFORMER: A transformer in which the primary and secondary are connected together in one winding.
• BATTERY: A. group of several cells connected together as a unit.
• BRANCH CIRCUIT: One of the conductors in a parallel circuit.
• BRUSH: The conducting material, usually a block of carbon, bearing against the commutator or slip-rings through which the current flows in or out.
• CATHODE: The electrode in a cell (voltaic or primary) that attracts the positive ions and repels the negative ions; the negative pole.
• CHOKE COIL: A coil of low ohmic resistance and comparatively high impedance to alternating current.
• -CIRCUIT: The complete path of an electric current including, usually, the generating device.
• CIRCUIT BREAKER: A device that opens a circuit while it is carrying current; often used in abnormal conditions, such as overloads.
• CIRCULAR MIL: An area equal to that of a circle with a diameter of 0.001 inch. It is used for measuring the cross section of wires.
• COMMUTATOR: That part of the armature of a dynamo which converts an alternating into a direct current.
• CONDENSER: A device consisting of two or more conductors separated by non-conductor material; it holds or stores an electric charge.
• CONDUCTANCE: The reciprocal of electrical resistance. Conducting power.
• CONDUCTIVITY: The ease with which a substance transmits electricity.
• CONDUCTOR: A material capable of transmitting electric current.
• CONVERTER, ROTARY: An electrical machine having a commutator at one end and slip-rings at the other end of the armature. It is used for the conversion of alternating to direct current.
• CORE: A mass of iron placed inside a coil to increase its magnetism.
• COULOMB: The-unit of static electricity; the quantity of electricity transferred by one ampere in one second.
• COUNTER EMF: Counter electromotive force; an EMF induced in a coil or armature that opposes the applied voltage.
• current OF ELECTRICITY: The continuous flow of electrons in a circuit.
• D'ARSONVAL GALVANOMETER: A galvanometer in which a moving coil swings between the poles of a permanent horseshoe magnet.
• DEMAGNETIZE: To deprive a body of its magnetic properties.
• DIELECTRIC: A non-conducting material.
• DIODE: A vacuum tube containing the filament and the plate; it serves as a rectifier of alternating current.
• DIP NEEDLE: A magnetized needle capable of rotation in a vertical plane.
• DIRECT current: An electric current that flows in one direction only.
• DYNAMO: A machine for converting mechanical energy into electrical energy or vice versa.
• EDDY current: A current induced in the core of an armature of a motor, dynamo, or transformer caused by changes in the magnetic field.
• EFFICIENCY: The ratio of a machine's useful work output to the total input.
• ELECTRODE: The terminal by which current leaves or enters an electrolytic cell.
• ELECTROLYTE: A substance that conducts a current by the movement of ions.
• ELECTROMAGNET: A magnet made by passing current through a coil of wire wound on a soft iron core.
• ELECTROMOTIVE FORCE (EMF): The electrical force that moves or tends to move electrons; ELECTRON: The smallest particle of negative electricity.
• ELECTROPLATING: The electrical method of plating a surface with a metal.
• ENERGY: The ability or capacity to do work.
• FIELD: The region where a magnet or electrical charge is capable of exerting its force.
• FIELD COIL: One of the coils used to excite a field magnet.
• FIELD MAGNET: The magnet used to produce a magnetic field (usually in motors or generators).
• FLUX: Magnetic lines of force, assumed to flow from the north pole to the south pole of a magnet.
• FREQUENCY: The number of cycles of an alternating current per second.
• FUSE: A part of a circuit made of a material that will melt and break the circuit when current is increased beyond a specific value.
• GALVANOMETER: An instrument used to measure small currents.
• GENERATOR: A machine that converts mechanical energy into electrical energy.
• GRID: A metal wire mesh placed between the cathode and plate.
• GRID BATTERY: The battery used to supply the desired potential to the grid.
• GRID LEAK: A very high resistance placed in parallel with the grid condenser.
• GROUND: A connection made directly to the earth or to a frame or structure which serves as one line of a circuit.
• HORSEPOWER: The English unit of power, equal to work done at the rate of 550 foot-pounds per second. Equal to 746 watts of electrical power.
• INDUCE: To produce an effect in a body by exposing it to the influence-of a magnetic force, an electric force, or a changing current.
• INDUCTION COIL: Two coils so arranged that an interrupted current in the first produces a voltage in the second.
• INTERRUPTER: A device for the automatic making and breaking of an electrical circuit.
• ION: An electrically charged atom.
• ISOGONIC LINE: An imaginary line drawn through points on the earth's surface where the magnetic deviation is equal.
• JOULE: A unit of energy or work. A joule of energy is liberated by one ampere flowing for one second through a resistance of one ohm.
• LAG: The number of degrees an alternating current lags behind voltage.
• LAMINATIONS: The thin sheets or discs making up an iron core.
• LEYDEN JAR: An early form of condenser.
• LINE OF FORCE: A line in a field of force that shows the direction of the force.
• LOAD: The energy delivered by a generator to its circuit.
• LODESTONE: A piece of magnetite.
• MAGNETIC CIRCUIT: The complete path followed by magnetic lines of force.
• MAGNETIC FLUX: The total number of lines of force issuing from a pole.
• MAGNETITE: An iron ore that is magnetic.
• MAGNETO: A generator in which the field is sup- plied by a permanent magnet.
• MEGOHM: A million ohms.
• MIL: One thousandth of an inch.
• MILLIAmmeter: An ammeter reading thousandths of an ampere.
• MILLIVOLTMETER: A voltmeter reading thousandths of a volt.
• MOTOR-GENERATOR (M-G): A generator driven by an electric motor.
• MUTUAL INDUCTION: The inducing of an EMF in a circuit by the field of a nearby circuit.
• NEGATIVE CHARGE: The electrical charge carried by a body which has an excess of electrons. (For example, a vulcanic rod, after it has been rubbed by fur or wool, carries a negative charge.)
• NEUTRON: A particle having the weight of a pro-ton but carrying no electric charge.
• NUCLEUS: The heavy or central part of an atom. OHMMETER: An instrument for directly measuring ohms.
• PERMALLOY: An alloy containing 78.5 percent nickel and 21.5 percent iron. It has an abnormally high magnetic permeability.
• PERMEABILITY: A property of matter that indicates the ease with which it is magnetized.
• PLATE current: The current that flows from the plate of a vacuum tube.
• POLARITY: The character of having magnetic poles, or electric charges.
• POLE: One of the ends of a magnet where most of its magnetism is concentrated.
• POSITIVE CHARGE: The electrical charge carried by a body which has become deficient in electrons. (For example, a glass rod, after it has been rubbed by silk, carries a positive charge.)
• POTENTIAL: The amount of charge held by a body.
• POWER: The time rate of doing work.
• PROTON: A positively charged, particle whose charge is equal, but opposite, to that of the electron.
• RECTIFY: To change an alternating current to a unidirectional or direct current.
• RELAY: An electrically operated device for the closing and opening of a circuit.
• RELUCTANCE: A measure of the resistance of a material to magnetic lines of force.
• resistance: The opposition of a conductor to an electric current.
• RETENTIVITY: The property of retaining magnetism.
• SATURATION, MAGNETIC: The condition of a magnetic substance when its magnetism has reached its highest possible value.
• SELF INDUCTION: The process by which a circuit induces an EMF in itself by its own magnetic field.
• SERIES CONNECTION: An arrangement of cells, generators, condensers, or conductor each carries the entire current of the circuit.
• SERIES-WOUND: Having the armature wired in series with the field winding. (Applied to motors or generators.)
• SOLENOID: A coil of wire used to produce a magnetic field.
• SPACE CHARGE: The charge acquired by the space inside a vacuum tube due to the presence of electrons.
• STEP-DOWN TRANSFORMER: A transformer with fewer turns in the secondary than in the primary.
• STEP-UP TRANSFORMER: A transformer with more turns in the secondary than in the primary.
• THERMOCOUPLE: A pair of metals which generate an EMF by the heating of one of the junctions; it is used to measure temperature differences.
• TRANSFORMER: A device that, without moving parts, transfers electrical energy from one circuit to another circuit by the aid of electromagnetic induction.
• TRIODE: A vacuum tube containing a filament, grid, and plate.
• UNIDIRECTIONAL: As applied to a current of electricity, a current that flows in one direction only.
• VACUUM TUBE: A tube from which the air has been pumped out. The tube contains an element that emits electrons when properly excited and an electrode to attract the electrons and set up a current in an external circuit.
• VOLT: The practical unit of electrical pressure.
• WATT: A unit of power produced by a current of one ampere at one volt.
• WATTMETER: An instrument for measuring electric power in watts.

Appendix Table II

ELECTRICAL FORMULAS

OHM'S LAW -
   For voltage ............... E = IR
   For current ............... I = E/R
   For resistance .......... R = E/I
 
POWER EQUATION -
   For power ................ P = IE
                                     P = I²R
                                     P = E²/R
   For current ............... I = P/E
   For voltage .............. E = P/I
 
COUNTER-EMF -
   For current .............. I = (E_a - E_g)/R_a

   For IR drop .............. IR = E_a - E_g

 
TRANSFORMERS -
   Voltage-turns .......... E_p/E_s = T_p/T_s

   current-turns .......... I_p/I_s = I_s/I_p

   Power ...................... I_pE_p = I_sE_s
                                
   Ampere-turns .......... I_pT_p = I_sT_s

 
SERIES CIRCUITS -
   For voltage ............... E_t = E₁ + E₂ + E₃ ...
   For current ............... I_t = I₁ = I₂ = I₃ ...
   For resistance .......... R_t = R₁ + R₂ + R₃ ...
 
PARALLEL CIRCUITS -
   For voltage .............. E_t = E₁ = E₂ = E₃ ...
   For current .............. I_t = I₁ + I₂ + I₃ ...
   For resistance ......... 1/R_t = 1/R₁ + 1/R₂ + 1/R₃ ...
 
HORSEPOWER -
   For hp ...................... hp = P/746
   For watts ................. P = 746 hp
 
¶ U.S. GOVERNMENT PRINTING OFFICE; 1945- 618779