Alternating current (advantages) -- As compared with DC, the advantage of AC is the reduced cost of transmission by use of high voltage transformers. 

Alternating currents (disadvantages) -- As compared with DC, the disadvantages of AC are: The high voltage which renders it dangerous and requires more efficient insulation; alternating current cannot be used for such purposes as electroplating, charging storage batteries, etc. 

Alternating current (effects) -- There are several effects of the AC to consider in determining the size of wires.  Accordingly, allowance must be made for: Self induction, mutual induction, power factor, skin effect, eddy currents,  frequency, resistance, electric hysteresis, etc.. 

Ammeter -- Measures the current flow in amperes in a circuit.  An ammeter is 
connected in series in the circuit. 

Ampere -- The practical unit of electric current flow.  If a one ohm resistance is 
connected to a one volt source, one ampere will flow. 

Anode -- The positive pole of a battery, or preferably the path by which the current passes out and enters the electrolyte on its way to the other pole; 
opposed to the cathode. 

Branch Circuit -- The circuit conductors between the final over current device 
protecting the circuit and the outlet(s). 

Calorie -- The French heat unit. 

Capacitance -- Measure, in farads, or the opposition to voltage changes in an AC circuit, causing voltage to lag behind current; exhibited by condensers, two conductors separated by a nonconductor. 

Capacitive Reactance -- The effect of capacitance in opposing the flow of alternating or pulsating current. 

Capacitor -- A device used to boost the voltage to a motor.  Running capacitors are used in starting winding to increase the running torque of the motor 
Starting capacitors are used in the starting winding to increase the starting torque of the motor.  Two electrodes or sets of electrodes in the form of plates, separated from each other by an insulating material called the dielectric. 

Circuit -- A complete path over which an electric current can flow. 

Circuit Breaker -- A device designed to open and close a circuit by non automatic means and to open the circuit automatically on a predetermined over current without injury to itself when properly applied within its rating.  Circuit breakers can be reset. 

Circuit (Series) -- A circuit supplying energy to a number of devices connected in series.   The same current passes through each device in completing its path to the source of supply. 

Close Circuit -- A circuit permitting a continuous current. 

Coil -- An assemblage of successive convolutions of a conductor.  A unit of a winding consisting of one or more insulated conductors connected in series and 
surrounded by common insulation, and arranged to link or produce magnetic flux. 

Conductance -- The measure of ease with which a substance conducts electricity, measured in ohms.  It is the opposite of resistance and is expressed in mhos. 

Conductor -- An electrical path which offers comparatively little resistance.  A wire or combination of wires not insulated from one another, suitable for 
carrying a single electric current.  Bus bars are also conductors.  Conductors may be classed with respect to their conducting power as; (a) good; silver, copper, aluminum, zinc, brass, platinum, iron, nickel, tin, lead; (b) fair; charcoal and coke, carbon, plumb ago, acid solutions, sea water, saline solutions, metallic ores, living vegetable substances, moist earth; (c) partial; water, the body, flame, linen, cotton, mahogany, pine, rosewood, lignum vitae, teak, and marble. 

Coulomb -- A unit of electrical charge; the quantity of electricity passing in one second through a circuit in which the rate of flow is one ampere. 

Cross -- Any accidental contact between electric wires or conductors. 

Current -- The movement of electrons through a conductor; measured in amperes, milliamperes, and microamperes. 

Cycle -- A complete reversal of alternating current, passing through a complete set of changes or motions in opposite directions, from a rise to maximum, return to zero, rise to maximum in the other direction, and another return to zero.  One 
complete positive and one complete negative alternation of current or voltage. 

Dead --  Free from any electric connection to a source of potential difference and from electric charge.  The term is used only with reference to current carrying parts that are sometimes alive. 

Deci -- A Latin prefix often used with a physical unit to designate a quantity one-tenth of that unit. 

Decibel -- Technically a measure of relative power levels.  (b) A measure of the loudness of a bell, siren, horn, or other noise.  (c) The strength of an audio signal. 

Deflection -- The distance or angle by which one line departs from another. 

Diagram -- A skeleton geometrical drawing, illustrating the principles of application of a mechanism. 

Diode -- A two electrode electron tube containing an anode and a cathode.  Diodes are used as rectifiers and detectors. 

Direct Current -- A unidirectional current.  It may be constant or periodically fluctuating, as rectified alternating current. 

Dissipation -- Loss of electric energy as heat. 

Drop -- The voltage drop developed across a resistor due to current flowing through it. 

E -- Symbol for voltage. 

Earth -- The ground considered as a medium for completing an electric circuit. 

Electrical Horsepower -- 746 watts. 

Electrical Units -- In the practical system, electrical units comprise the volt, the 
ampere, the ohm, the watt, the watt-hour, the coulomb, the henry, the mho, the joule, and the farad. 

Electric Circuit -- The path (whether metallic or nonmetallic) of an electric current. 

Electrician -- A person who is versed in the knowledge of electricity. 

Electricity -- The name is given to an invisible agent known only by its effects and manifestations, as shown in electrical phenomena.  Electricity, no matter how produced is believed to be one and the same thing. 

Electrocution -- The destruction of life by means of electric current. 

Electromagnet -- A magnet produced by passing an electric current through and insulated wire conductor coiled around a core of  soft iron, as in the fields of a dynamo or motor. 

Electromotive Force (EMF) -- An energy-charge relation that results in electric pressure (voltage), which produces or tends to produce charge flow. 

Electron -- The smallest charge of negative electricity known. 

Energy Efficiency -- The efficiency of an electric machine measured in watt hours or kilowatt hours; the watt hour efficiency. 

Farad -- Practical unit of electrostatic capacity in the electromagnetic system.  A 
condenser is said to have a capacity of one farad if it will absorb one coulomb ( that is, one ampere per second), of electricity when subjected to a pressure of one volt.  The unit of capacitance. 

Faraday Effect -- A discovery made by Faraday that a wave of light polarized in a certain plane can be turned about by the influence of a magnet so that the vibrations occur in a different plane. 

Fathom -- A measure of  length equal to six feet, used chiefly in taking soundings, measuring cordage, etc. 

Fiber Optics -- Piping light is the science that deals with the transmission of light 
through extremely thin fibers of glass, plastic, or other transparent material. 

Fluorescence -- That property by virtue of which certain solids and fluids become luminous under the influence of radiant energy. 

Force -- An elementary physical cause capable of modifying the motion of a mass. 

Formula -- A prescribed form, principle, or rule expressed in mathematical terms, chemical symbols, etc. 

Formulae  -- A rule or principle expressed in algebraic language. 

Frequency -- The number of periods occurring in the unit of time periodic process, such as in the flow of electric charge.  The number of complete cycles per second existing in any form of wave motion; such as the number of cycles per second of an alternating current. 

Fuse -- A strip of wire or metal inserted in series with a circuit which, when it carries an excess of current over its rated capacity, will burn out.  Also called a 
cutout. 

Galvanometer -- A current indicator.  It consists of a magnetic needle suspended within a coil of wire and free to swing over the face of a graduated dial.  The movement of the needle shows the direction of the current and indicates whether it is a strong or weak one.  There are numerous types of galvanometers such as; astatic, tangent, sine, differential, ballistic, and D’Arsonval. 

Generator -- A general name given to a machine for transforming mechanical energy into electrical energy. 

Ground -- A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of the earth. 

Grounded -- Connected to earth or to some conducting body that serves in place of the earth. 

Heat (electric) -- The heat produced in a conductor by the passage of an electric current through it. 

Horsepower (hp) -- Unit used to express rate of work, or power.  One 
horsepower=746 watts.  Work done at the rate of 33,000 foot pounds per 
minute or 550 foot pounds per second. 

I -- Symbol for electric current. 

Impedance -- The total opposition which a circuit offers the flow of alternating current at a given frequency; combination of resistance and reactance, measured 
in ohms. 

Induction -- The process by which an electrical conductor becomes electrified when near a charged body and becomes magnetized. 

Input -- The intake or energy absorbed by a machine during its operation, as 
distinguished from the output of useful energy delivered by it. 

Insulator -- A device for fastening and supporting a conductor.  Glass and porcelain are employed almost universally for supporting overhead wires. 

Ion -- An electrically charged atom or radical. 

Jacobi’s Law -- A law of electric motors which states that the maximum work of a motor is performed when its counter electromotive force is equal to one half the electromotive force expended on the motor. 

Joint -- The tying together of two single wire conductors so that the union will be good, both mechanically and electrically. 

Joule's Law -- The law first stated by Joule, that the quantity of heat developed in a conductor by the passage of an electric current is proportional to the resistance of  the conductor, to the square of the strength of the current, and to the duration of the flow. 

Kilovolt (kv) -- A unit of pressure equal to one thousands volts. 

Kilowatt -- A unit of electrical power, equal to one thousands watts. Electric power is usually expressed in kilowatts.  As the watt is equal to 1/746 
horsepower, the kilowatt or 1,000 watts = 1.34 hp.  Careful distinction should be made between kilowatts and kilovolt amperes. 

L -- The symbol for inductance. 

Leakage -- The escape of electric current through defects in insulation or other causes. 

Loss -- Power expended without accomplishing useful work. 

Made Circuit -- A closed or completed circuit. 

Mega-Volt -- A unit of pressure equal to one million volts. 

Meter -- An electric indicating instrument as a voltmeter, ammeter, etc. 

Negative -- The opposite of positive.  A potential less than that of another potential or of the earth.  In electrical apparatus,  the pole or direction toward 
which the current is suppose to flow. 

Network -- An electric circuit in which the parts are connected in some special manner and cannot be classed as in series, in parallel, or in series-parallel. 

Neutron -- A proton and an electron in very close union existing in the nucleus.  A particle having the weight of a proton but carrying no electric charge. It is located in the nucleus of an atom. 

Ohm -- The unit of electrical resistance.  Resistance is one ohm when a DC voltage of one volt will send a current of one ampere through. 

Open Circuit -- A circuit, the electrical continuity of which has been interrupted, as by opening a switch. 

Output -- The current, voltage, power, or driving force delivered by a circuit or device. 

P -- Abbreviation for power. 

Peak -- The maximum instantaneous value of a varying voltage or current. 

Peak Current -- The maximum value of an alternating current. 

Period -- The time required for a complete cycle of alternating current or voltage; for 60 cycles per second, a period would be 1/60 second. 

Photoelectric -- Descriptive of the effect which light has on electric circuits, through a device controlled by light. 

Positive -- The term used to describe a terminal with fewer electrons than normal so that it attracts electrons.  Electrons flow into the positive terminals of a voltage source. 

Power -- The rate at which work is done; it is usually expressed as the number of foot pounds in one minute, that is, if you lift 33,000 foot pounds in one minute, you have done 1 horsepower of work. 

Proton -- The smallest quantity of electricity which can exist in the free state.  A positive charged particle in the nucleus of an atom. 

Quick-Break -- A switch or circuit breaker that has a high contact opening speed. 

R -- Symbol for resistance. 

Reactance -- Opposition offered to the flow of AC by the inductance or capacity of a part; measured in ohms. 

Recovery Voltage -- The voltage impressed upon the fuse after a circuit is cleared. 

Relay -- An electromagnetic device which permits control of current in one circuit by a much smaller current in another circuit. 

Resistance -- The opposition offered by a substance or body to the passage through it of an electric current which converts electric energy into heat. 
Resistance is the reciprocal of conductance. 

Resistance Drop -- The voltage drop in place with the current. 

Resistor -- An aggregation of one or more units possessing the property of electrical resistance.  Resistors are used in electric circuits for the purpose of 
operation, protection, or control. 

Semiconductor -- A name given to substances having only moderate power 
of transmitting electricity, and which may be said in that respect to, stand midway between conductors and insulators. 

Series Circuit -- A circuit supplying energy to a number of loads connected in series, that is, the same current passes through each load in completing its 
path to the source of supply. 

Series Parallel Circuit -- An electric current containing groups of parallel connected receptive devices, the groups being arranged in the circuit in series; a 
series multiple circuit. 

Short Circuit -- A fault in an electric circuit or apparatus due usually to imperfect insulation, such that the current follows a by-path and inflicts damage or is wasted. 

Solenoid -- A spiral of conducting wire, would cylindrically so that when an electric current passes through it, its turns are nearly equivalent to a succession of parallel circuits, and it acquires magnetic properties similar to those of a bar magnet. 

Spark -- A discharge of electricity across a gap between two electrodes.  The discharge is accompanied by heat and incandescence.  Distinguish between spark and arc. 

Steady Current -- An electric current of constant amperage. 

Switch -- A device for making, breaking, or changing the connections in an electric current. 

Telsa Coil -- A form of induction coil designed by Telsa for obtaining high voltages and frequencies; it consists of a primary of a few turns of coarse wire and a secondary of fine wire, both immersed in oil insulation; a Telsa transformer. 

Transformer -- An apparatus used for changing the voltage and current of an 
alternating circuit.  A transformer consists of primary winding, secondary winding, and an iron core.  In principle, if a current is passed through a coil of wire encircling a bar of soft iron, the iron will become a magnet; when the current is  is continued the bar loses its magnetization. 

Transistor -- An active semiconductor device with three or more terminals.  Transistors turn on instantly.  They don't require a warm-up time like a tube does. 
A transistor will last for years and very little voltage is needed. 

Unit of Current -- The practical unit of current is the ampere, which is the current produced by a pressure of one volt in a circuit having a resistance of one ohm. 

Unit of Electric Work -- The joule. 

Unit of Pressure -- The volt, or pressure which will produce a current of one ampere against a resistance of one ohm. 

Unit of Resistance -- The ohm, which is the resistance that permits a flow of one ampere when the impressed pressure is one volt. 

V -- Symbol for volt. 

Volt -- The practical unit of electric pressure.  The pressure which will produce a current of one ampere against a resistance of one ohm. 

Voltage Drop -- The drop of pressure in an electric circuit due to the resistance of the conductor. 

V-O-M meter -- Volt-ohm-milliammeter, the troubleshooters'' basic testing instrument. 

W -- Symbol for wattage. 

Watt -- The practical unit of power, being the amount of energy expended per second by an unvarying current of one ampere under the pressure of one volt. 

X -- Symbol for reactance. 

Y connection -- This method of transformer connection consists in connecting both the primaries and secondaries in star grouping. 

Z -- Symbol for impedance.