Download 10-1 GLOSSARY TO TERMS A - Abbreviation for ampere. Absolute

GLOSSARY TO TERMS
A - Abbreviation for ampere.
Absolute Value - The value of a number without regard to the sign.
AC - Abbreviation for alternating current.
Adjustable Resistor - A resistor whose value can be verified.
Alloy - A mixture of two or more metals.
Alternating Current - Is current flow whose direction reverses at fixed intervals and varies in intensity from zero
to some positive value then reduces to zero and rises in intensity to some negative value
before again reducing to zero.
Alternator - The simplest type of machine for producing an alternating voltage and current.
Ammeter - An instrument for measuring the amount of current flowing in a circuit.
Ampere - The unit of electron flow through a conductor.
Ampere Hour - A measure of the amount of current that a battery can deliver steadily for a given period of time.
Ampere Turn - The magnetizing force produced by a current of one ampere flowing through a coil of one turn.
Amplifier - Any device that will receive at it’s input a signal of given amplitude of voltage and deliver at it’s
output a signal of greater amplitude.
Amplitude - The size of a signal. Generally used to describe voltage, current or power.
Anode - A positive electrode of an electrochemical device toward which the negative ions are drawn.
Apparent Power - The power apparently available for use in an AC circuit containing a reactive element. It is
the product of effective voltage times effective current expressed in volt-amperes. It must be
multiplied by the power factor to obtain true power available.
Armature - Consists essentially of coils of wire wrapped around a soft iron core from which electric current is
induced in a generator.
Atom - Is the smallest particle of an element that retains the characteristics of that element. Is composed of
electrons, protons and neutrons.
Autotransformer - A transformer in which the primary and secondary coils have part or all of their turns in
common.
Balanced Load - A three phase load which draws equal current from each phase.
Base - The element in a transistor which controls the flow of current carriers. The base is always sandwiched
between the emitter and collector and is considerably thinner than either. It is lightly doped to provide it
with few majority carriers.
Battery - A device for converting chemical energy into electrical energy. Consists of two or more cells.
Bias - A difference of potential that exists between the cathode and grid for the purpose of controlling current.
10-1
Branch Circuit - An individual current path in a circuit. Each branch carries a portion of the total current.
Break-Down Voltage - The highest voltage pressure that the device can hold back when it is turned off. The
phenomenon occurring in a reversed biased semiconductor diode as a transition from a
high dynamic resistance to one of lower dynamic resistance. This is done to boost the
reverse current.
Bridge Rectifier - A rectifier designed to provide the same peak voltage as a half-wave rectifier and the same
ripple frequency as the full-wave rectifier.
Brush - The conducting material, usually a block of carbon bearing against the commutator or sliprings through
which the current flows in or out.
Brushless Generator - A machine that produces power without the use of sliprings or brushes by employing a
rotating field and the output power is taken off stationary windings.
Bus - A primary power distribution point connected to the main power source.
C - The letter which stands for capacitance.
Cable - An assembly of electrical conductors insulated from each other but laid up together usually by being
twisted around a central core.
Calibration - The act of comparing an instrument with a standard to determine it’s accuracy.
Capacitance - The property of an electrical circuit that opposes changes in voltage. The property of a capacitor
that enables it to store and release electrons. The capacitor is said to have a capacitance of one
farad when a change of one volt per second produces a current of one ampere.
Capacitive Reactance - The opposition to the flow of an alternating current by capacitance, expressed in ohms.
Capacitor - Electrical device which is commonly used to smooth out irregular pulses in electrical current,
allowing more constant flow of electrons. An electrical device capable of storing electrical energy
in an electrostatic field.
Cathode - The general name for any negative electrode. The negative terminal of a forward-biased semiconductor diode which is the source of the electrons.
Cell - A single unit that transforms chemical energy into electrical energy.
Centrifugal Switch - A switch found on a motor shaft which is operated by the force created on it by spinning
around.
Charge - Represents electrical energy. A material having an excess of electrons is said to have a negative charge
and a material having an absence of electrons is said to have a positive charge. A quantity of electrons
stored on the plates of a capacitor.
Choke Coil - A coil of low ohmic resistance and high impedance to alternating current and low resistance to
direct current.
Circuit - The complete path of an electric current.
Circuit Breaker - An electromagnetic or thermal device that opens a circuit when the current in the circuit
exceeds a predetermined amount. Circuit breakers can be reset.
10-2
Circular Mil - An area equal to that of a circle with a diameter of .001 inch. It is used for measuring the cross
section of wires.
Coil - An inductive device created by looping turns of wire around a core.
Collector - The element in a transistor which collects the current carriers.
Commutator - The copper segments on the armature of a motor or generator. It is cylindrical in shape and is
used to pass power into or from the brusher.
Conductance - The ability of a material to conduct or carry an electric current. It is the reciprocal of the
resistance of the material and is expressed in ohms or siemens.
Conductivity - The ease in which a substance transmits electricity.
Conductor - A material with a large number of free electrons. A material which easily permits electric current
to flow.
Continuity Check - A test with an ohmmeter to make sure there is an uninterrupted circuit for current to flow.
Copper - The most commonly used conductor.
Core - Any material that affords a path for magnetic flux lines in a coil. The center of a coil or transformer
normally air or iron.
Coulomb - A measure of the quantity of electricity. One coulomb is equal to 6.28 x 10 to the 18 power.
Counter EMP - An EMF induced in a coil or armature that opposes the applied voltage.
Current - The drift of electrons past a reference point. The passage of electrons through a conductor. Measured
in amperes.
Current Transformer - A transformer used to step down line currents in a known ratio to permit the use of lower
range instruments and to isolate components or instruments from high voltages.
Cycle - One complete negative and positive alternation of a current or voltage.
Delta Connection - When a three phase stator is connected so that the phase voltage and the end of one phase is
connected to the start of another phase.
Dielectric - An insulator; a term that refers to the insulating material between plates of a capacitor.
Dielectric Constant - The ration of the capacitance of a capacitor with a dielectric between the electrodes to the
capacitance of a capacitor with air between the electrodes.
Dielectric Leakage - Power loss of a capacitor due to the leakage of current through the dielectric.
Diode - Simply means having to electrons. A semi-conductor device which permits electrons to flow through it
in one direction only. Used to rectify or as a switching device.
Direct Current - An electric current that flows in one direction only. Abbreviated - DC.
Dry Cell - An electric cell in which the electrolyte is not a liquid.
Dynamo - A machine for converting mechanical energy into electrical energy (generator).
10-3
Eddy Current - Induced circulating currents in a conducting material that are caused by a varying magnetic
field.
Effective Current - The equivalent heating value of an alternating current or voltage as compared to a direct
current or voltage. It is .707 times the peak value of a sine wave.
Efficiency - The ratio of output power to input power usually expressed as a percentage.
Electric Current - The flow of electrons.
Electrical Charge - Electric energy stored in or on an object. The negative charge is caused by an excess of
electrons; the positive charge caused by a deficiency of electrons.
Electrochemical - The action of converting chemical energy into electrical energy.
Electrode - The terminal at which electricity passes from one medium into another such as in an electric cell
where the current leaves or returns to the electrolyte.
Electrolyte - A solution of a substance which is capable of conducting electricity. An electrolyte may be in
the form of either a liquid or a paste.
Electromagnet - A magnet made by passing electric current through a coil of wire wound on a soft iron core.
Electromagnetic Induction - The production of a voltage in a coil due to a change in the number of magnetic
lines passing through the coil.
Electromotive Force - The force that produces an electric current in a circuit.
Electron - The elementary negative charge that revolves around the nucleus of an atom.
Electron Shell - A group of electrons which have a common energy level that forms part of the outer structure
of an atom.
Electrostatic - Pertaining to electricity at rest such as charges on an object.
Electrostatic Field - The field of influence between two charged bodies.
Element - A substance, in chemistry, that cannot be divided into simpler substances by any means ordinarily
available.
Emitter - The element in a transistor that emits current carriers.
Energy - The ability or capacity to do work.
Exciting Current - The current that flows in the primary winding of a transformer which produces magnetic
flux field. Also called a magnetizing current.
Extrinsic - A semi-conductor in which impurities have been added to create certain charge carrier
concentration.
Farad - The basic unit of capacitance. A capacitor has a capacitance of 1 farad when a voltage change of one
volt per second across it produces a current of one ampere.
Feedback - A transfer of energy from the output circuit of a device back to its input.
10-4
Fidelity - The quality of reproducing an output signal exactly like the input signal except for amplitude and
sometimes phase. (Output and input signals exactly alike in terms of frequency and shape.)
Field - Space containing electric of magnetic lines of force.
Field Winding - The coil used to provide the magnetizing force in motors and generators.
Filter - A selective network of resistors, capacitors, and inductors which offer little opposition to certain
frequencies or to direct current while blocking or attenuating other frequencies.
Fixed Bias - A constant value of a bias voltage.
Fixed Resistor - A resistor having a definite resistance value.
Flux - In electrical or electromagnetic devices a general term used to designate, collectively, all the electric
or magnetic lines of force in a region. A substance used to prevent oxidation during soldering.
Forward Voltage - In a diode, the amount by which anode voltage exceeds cathode voltage. (Anode more
positive than cathode.)
Forbidden Band - The energy band in an atom lying between the conduction band and the valence band.
Electrons are never found in the forbidden band but may travel back and forth through it.
The forbidden band determines whether a solid material will act as a conductor, semiconductor or an insulator.
Forward Bias - An external voltage that is applied to a PN junction; offers only minimum resistance to the flow
of current. Conduction is by majority current carrier (holes in P-type material and electrons in
N-type material).
Forward Current - The amount of conventional current flowing from cathode to anode when a given reverse
voltage is imposed on a diode.
Free Charges - Those electrons that can be moved by externally applied voltages.
Free Electrons - Electrons which are loosely held and consequently tend to move at random among the atoms
of the material.
Frequency - 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. Formally expressed in cps. Also expressed in (Hz)
hertz, (kHz) kilohertz, (Mhz) megahertz and (Ghz) gigahertz.
Frequency Determining Network - A circuit that provides the desired response (maximum or minimum
impedance) at a specific frequency.
Frequency Response - The gain of an amplifier plotted against the frequency of the signal being amplified.
Full Wave Rectifier - A circuit which uses both positive and negative alternations in an alternating current to
produce direct current.
Fuse - A protective device inserted in series with a circuit it contains a metal which melts or breaks when current
is increased beyond a specific value for a definite period of time.
Gamma - The emeter to base current ratio in a common collector configuration.
Galvanometer - An instrument used to measure small DC currents.
10-5
Gain - Ratio of output signal to input signal. For an NPN or PNP transistor, the type of gain specified in data
sheets is current gain and often called “beta”.
Gaseous - One of three states of matter having no fixed form or volume.
Gate - The control terminal and controlling region of a field effect transistor. Corresponds to base of bipolar
transistor.
Generator - A machine that converts mechanical energy into electrical energy.
Germanium - A grayish white metal having semi-conductor properties. In its solid state, germanium can be
considered as a crystalline structure in which atoms combine in the form of a lattice with each
atom bound to each of the adjacent atoms by electronic force. Germanium atoms have four
valence electrons; each of the four enters into a covalent bond with an electron from four adjacent
atoms.
Graph - A pictorial presentation of the relation between two or more variable quantities, such as between an
applied voltage and the current it produces in a circuit.
Ground - A metallic connection with the earth to establish ground potential. Also a common return to a point
of zero potential.
Ground Potential - Zero potential with respect to the ground or earth.
Half Wave Rectifier - A rectifier using only one-half of each cycle to change AC to pulsating DC.
Henry - The electromagnetic unit of inductance or mutual inductance. The inductance of a circuit is 1 henry
when a current variation of 1 ampere per second induces 1 volt. It is the basic unit of inductance.
Hertz - A unit of frequency equal to once cycle per second.
Hole Flow - In the valence band a process of conduction in which electrons move into holes thereby creating
other holes which appear to move toward a negative potential. (The movement of holes is
opposite the movement of electrons.)
Horsepower - The English unit of power; equal to work done at the rate of 550 ft. lbs. per second. Equal to 746
watts of electrical power.
Hydrometer - An instrument used to measure specific gravity. In batteries, hydrometers are used to indicate the
state of charge by the specific gravity of the electrolyte.
Impedance - The total opposition offered to the flow of an alternating current. It may consist of any
combination of resistance, inductive reactance and capacitive reactance. The symbol for
impedance is Z.
Induced Charge - An electrostatic charge produced on an object by the electric field that surround a nearby
object.
Induced Current - Current due to the relative motion between a conductor and a magnetic field.
Induced Voltage - The electromotive force induced in a conductor due to the relative motion between a
conductor and a magnetic field.
Inductance - The property in a circuit which tends to oppose a change in the existing current.
10-6
Induction - The act or process of producing voltage by the relative motion of a magnetic field across a
conductor.
Inductive Reactance - The opposition to the flow of alternating or pulsating current caused by the inductance
of a circuit. It is measured in ohms.
Insulator - Material of such low conductivity that the flow of current through it can usually be neglected.
Integrated Circuit - A circuit in which many elements are fabricated and interconnected by a single process as
opposed to a non-integrated circuit in which transistors, diodes, resistors and other
components are fabricated separately and then assembled.
Ion - An electrically charged atom or group of atoms.
Ionization - The electrically charged particles produced by high energy radiation such as light or ultraviolet
rays or by the collision of particles during thermal agitation.
Junction - The connection between two or more conductors. The contact between two dissimilar metals or
materials as in a thermocouple.
Junction Diode - A two terminal device containing a single crystal of semi-conducting material which ranges
from P-type at one terminal to N-type at the other.
Junction Transistor - A bipolar transistor constructed from interacting PN junctions. The term is used to
distinguish junction transistors from other types such as FET and point contact.
Kilo - A prefix meaning 1000.
Kinetic Energy - Energy which a body possesses by virtue of its motion.
Kirchoff’s Law - The algebraic sum of the currents flowing toward any point in an electric network is zero. The
algebraic sum of the products of the current and resistance in each of the conductors in any
closed path in a network is equal to the algebraic sum of the electromotive forces in the path.
Lag - The amount one wave is behind another in time; expressed in electrical degrees.
Laminated Core - A core built up from thin sheets of metal insulated from each other and used in transformers.
Law of Magnetism - Like poles repel; unlike poles attract.
Lead - The amount one wave is ahead of another in time. A wire or connection. A heavy soft metal with a low
melting point mixed with tin to form solder.
Lead Acid Cell - A cell in an ordinary storage battery in which electrodes are grids of lead containing an active
material consisting of certain lead oxides that change in composition during charging and
discharging. The electrodes or plates are immersed in an electrolyte of diluted sulfuric acid.
Leakage Flux - Magnetic flux lines produced by the primary winding which do not link the turns of the
secondary winding.
Leakage Resistance - The electrical resistance which opposes the flow of current through the dielectric of a
capacitor. The higher of the leakage resistance the slower the capacitor will discharge or
leak across the dielectric.
Left Hand Rule for Generators - A rule or procedure used to determine the direction of current flow in a
generator.
10-7
Lenz’s Law - The current induced in a circuit due to its motion in a magnetic field or to a change in its
magnetic flux in such a direction as to exert a mechanical force opposing the motion or to
oppose the change in flux.
Light Emitting Diode - A PN junction which emits visible light when it is forward biased. Depending on the
material used to make the diode the light may be red, amber or green.
Linear - Having an output that varies in direct proportion to the input.
Linear Integrated Circuit - An amplifying type integrated circuit.
Line Drop - The voltage drop between two points on a power line due to the resistance of the line.
Line of Force - A line in an electric or magnetic field that shows the direction of the force.
Liquid - One of three states of matter which has a definite volume but no definite form.
Load - A device through which an electric current flows and which changes electrical energy into another
form. Power consumed by a device or circuit in performing its function.
Logarithm - The power that the base must be raised to in order to get the number.
Magnetic Amplifier - An amplifier that uses electromagnetic effects to provide amplification of a signal.
The magnetic amplifier uses a changing inductance to control the power delivered to
the load.
Magnetic Circuit - The complete path of magnetic lines of force.
Magnetic Field - Region in which the magnetic forces created by a permanent magnet or by a current
carrying conductor or coil can be detected.
Magnetic Lines of Force - Imaginary lines used for convenience to designate the direction in which magnetic
forces are acting as a result or magnetic-motive force.
Magnetic Poles - The section of a magnet where the flux lines are concentrated; also where they enter and
leave the magnet.
Magnetism - The property possessed by certain materials by which these materials can exert mechanical force
on neighboring masses of magnetic materials and can cause currents to be induced in conducting
bodies moving relative to the magnetized bodies.
Magnetize - To convert a material into a magnet by causing the molecules to rearrange.
Magneto - A generator which produces alternating current and has a permanent magnet as its field.
Magnitude - The size or numerical value of a wave form.
Majority Carriers - The mobile charge carriers which are predominate in a semi-conductor material.
Matter - Any physical entity which possesses mass.
Maximum Power Dissipation - Semi-conductor specification relating to the amount of heat the device can stand
before it malfunctions. This is sometimes expressed in terms of current as
maximum forward current as maximum for diodes and maximum collector
current for transistors.
10-8
Mega - A prefix meaning 1 million.
Megger - A test instrument used to measure insulation resistance and other high resistances. It is a portable,
hand-operated DC generator used as an ohmmeter.
MHO - Unit of conductance; the reciprocal of the ohm.
Micro - A prefix meaning one millionth.
Microelectronics - The solid state concept of electronics in which compact semi-conductor materials are
designed to function as an entire circuit or sub-assembly rather than as circuit components.
Milli - A prefix meaning one thousandth.
Minority Carriers - Either electrons or holes, whichever is the less dominate carrier in a semi-conductor device.
In P-type devices electrons are minority. In N-type devices the holes are minority.
Minority Current - A very small current that passes through the base to collector junction when this junction is
reverse biased.
Modular Circuitry - A technique where printed circuit boards are stacked and connected together to form a
module.
Monocrystalline - Made up of a single, continuous crystal. This is the form required for semi-conductor
material used in electronic devices.
Monolithic Circuit - A circuit where all elements associated with the circuit are fabricated inseparably within
a continuous piece of material usually silicon.
Motor-Generator - A motor and a generator with a common shaft used to convert line voltages to other
voltages or frequencies.
Mutual Flux - The total flux in the core of a transformer that is common to both the primary and secondary
windings. The flux links both windings.
Mutual Inductance - A circuit property existing when the relative position of two inductors causes the
magnetic lines of force from one link with the turns of the other. The symbol for mutual
inductance is M.
Negative Alternation - The negative half of an AC wave form.
Negative Charge - The electrical charge carried by a body which has an excess of electrons.
Negative Electrode - A terminal or electrode having more electrons than normal.
Negative Feedback - Feedback in which the feedback signal is out of phase with the input signal.
Network - A combination of electrical components. In a parallel circuit it is composed of two or more
branches.
Neutral - In a normal condition neither positive nor negative.
Neutralization - The process of counteracting the effects interelectrode capacitance.
Neutron - A particle having the weight of a proton but carrying no electric charges. It is located in the nucleus
of an atom.
10-9
Non-linear - Having an output that does not rise and fall directly with the input.
NPN - An NPN transistor is formed by introducing a thin region of P-type material between two regions of
N-type material.
Nucleus - The central part of an atom that is mainly comprised of protons and neutrons. It is the part of the
atom having the most weight.
Null - Zero.
Ohm - The unit of electrical resistance. It is that value of electrical resistance through which a constant
potential difference of one volt across the resistance will maintain a current flow of one ampere
through the resistance.
Ohmic Value - Resistance in ohms.
Ohmmeter - An instrument for directly measuring resistance in ohms.
Ohm’s Law - The current in an electric circuit is directly proportional to the electromotive force in the circuit.
The most common form of the law is E=IR, where E is the electromotive force or voltage across
the circuit, I is the current flowing in the circuit and R is the resistance of the circuit.
Open Circuit - The condition of an electrical circuit caused by the breaking of one or more conductors of the
circuit. A circuit which does not provide a complete path for current to flow.
Operational Amplifier (Op Amp) - An amplifier designed to perform computing or transfer operations and
which has the following characteristics: Very high gain, very high input
impedance and very low output impedance.
Oscillator - An amplifying type circuit function whose output is a regularly fluctuating current or voltage.
Overload - A load greater than the rated load of an electrical device.
Parallel Circuit - Two or more electrical devices connected to the same pair of terminals so separate currents
flow through each.
Peaking Coil - An inductor used in an amplifier to provide high frequency compensation which extends the
high frequency response of the amplifier.
Peak-to-Peak - The measure of absolute magnitude of an AC wave form measured from the greatest positive
alteration to greatest negative alteration.
Peak Value - The maximum instantaneous value of a varying current, voltage or power. It is equal to 1.414
times the effective value of a sine wave.
Permeability - The measure of the ability of a material to act as a path for additional magnetic lines of force.
Phase - The angular relationship between two alternating currents or voltages when the voltage or current is
plotted as a function of time. When the two are in the phase the angle is zero and both reach their peak
at the same time. When out of phase, one will lead or lag the other at the instant one is at its peak, the
other will not be at peak value and may differ in polarity as well as magnitude.
Phase Angle - The number of electrical degrees of lead or lag between the voltage and current wave forms in
an AC circuit.
Phase Difference - The time in electrical degrees by which one wave leads or lags another.
10-10
Plate - One of the electrodes in a storage battery.
Positive Alteration - The positive half of an AC wave form.
Potentiometer - A 3-terminal resistor with one or more sliding contacts which functions as an adjustable
voltage divider.
Power - The rate of doing work or the rate of expending energy. The unit of electrical is the watt.
Power Amplifier - An amplifier in which the output signal power is greater than the input signal power.
Power Factor - The ratio of the actual power of an alternating or pulsating current as measured by a wattmeter to
the apparent power as indicated by an ammeter and voltmeter readings. The power factor of an
inductor, capacitor or insulator is an expression of their losses.
Power Supply - A unit that supplies electrical power to another unit.
Primary Cell - An electrochemical cell in which the chemical eats away one of the electrodes usually the
negative electrode.
Primary Winding - The winding of a transformer connected to the electrical source.
Printed Circuit Board - A flat, insulating surface which printed wiring and miniaturized components are
connected in a predetermined design and attached to a common base.
Push Pull Amplifier - An amplifier which uses two transistors whose output signals are combined to provide
a larger gain than a single transistor can provide.
Ratio - The value obtained by dividing one number by another indicating their relative proportions.
Reactance - The opposition offered to the flow of an AC by the inductance, capacitance or both in any circuit.
Reciprocal - The value obtained by dividing the number one by any quantity.
Rectifier - A device which by its conduction characteristics converts alternating current to a pulsating direct
current.
Reference Point - A point in a circuit to which all other points in the circuit are compared.
Regulator - The section in a basic power supply that maintains the output of the power supply at a constant
level in spite of large changes in load current or the input line voltage.
Reluctance - A measure of the opposition that a material offers to magnetic lines of force.
Repulsion - The mechanical force tending to separate bodies having like electrical charges or like magnetic
polarity.
Residual Magnetism - Magnetism remaining in a substance after removal of the magnetizing force.
Resistance - The property of a conductor which determines the amount of current that will flow as the result of
the application of a given voltage. The opposition which a device or material offers to the flow of
current. The effect of resistance is to raise the temperature of the material or device carrying the
current.
Resistor - The electrical component which offers resistance to the flow of current.
10-11
Resonance - The condition existing in a circuit when the values of inductance, capacitance and the applied
frequency are such that the inductive reactance and capacitive reactance cancel each other.
Retentivity - The ability of a material to retain its magnetism.
Reverse Bias - When an external voltage is applied to a PN junction and the junction offers a high resistance
to current flow.
Rheostat - A resistor whose value can be varied. A variable resistor which is used for the purpose of adjusting
current in a circuit.
Root Mean Square (RMS) - The equivalent value of an alternating current or voltage as compared to a direct
current or voltage. It is .707 times the peak value of a sine wave.
Saturation - The condition in which a magnetic material has reached a maximum flux density and the
permeability has decreased to a value of approximately 1.
Saturable Core Conductor - A coil whose reactance is controlled by changing the permeability of the core.
Schematic Circuit Diagram - A circuit diagram in which component parts are represented by simple, easily
drawn symbols.
Schematic Symbols - A letter, abbreviation or design used to represent specific characteristics or components
on a schematic diagram.
Secondary - The output coil of a transformer.
Secondary Cell - A cell that can be recharged by passing a current through the cell in a direction opposite to the
discharge current.
Selenium - A chemical element which has rectification and light sensitive properties which make it widely
used as a semi-conductor material.
Series Circuit - An arrangement where electrical devices are connected so that the total current must flow
through all the devices; electrons have only one path to travel from the negative terminal to the
positive terminal.
Series-Parallel Circuit - A circuit that consists of both series and parallel circuits.
Shelf Life - The period of time that a cell or battery may be stored and still be useful.
Shielding - A metallic covering used to prevent magnetic or electromagnetic fields from affecting an object.
Short Circuit - A low resistance connection between two points of different potential in a circuit usually
accidental and usually resulting in excessive current flow that may cause damage.
Signal - A general term used to describe any AC or DC of interest in a circuit.
Silicon - A metallic element which in its pure state is used as a semi-conductor.
Silicon Controlled Rectifier - A semi-conductor device that functions as an electrically controlled rectifier.
Sine Wave - The curve traced by the projection on a uniform time scale of the end of a rotating arm or
vector. Also known as a sinusoidal wave.
10-12
Solenoid - An electromagnetic coil that contains a moveable plunger.
Solid - One of the three states of matter which has definite volume and shape.
Solid State Device - An electronic device which operates by the movement of electrons within a solid piece
of semi-conductor material.
Source Voltage - The device which furnishes the electrical energy used by a load.
Specific Gravity - The ratio between the density of a substance and that of pure water at a given temperature.
Static Electricity - Stationary electricity that is in the form of a charge. The accumulated electric charge on an
object.
Switch - A device to connect, disconnect or change the connection in an electrical circuit.
Synchroscope - An instrument used to indicate a difference in frequency between two AC sources.
Tachometer - An instrument for indicating revolutions per minute.
Temperature Coefficient - The amount of change of resistance in a material per unit change in temperature.
Terminal - An electrical condition.
Thermistor - A resistor that is used to compensate for temperature variations in a circuit.
Thermocouple - A junction of two dissimilar metals that produces a voltage when heated.
Tolerance - The maximum error or variation from the standard permissible in a measuring instrument.
Torque - The turning effort or twist which a shaft sustains when transmitting power.
Total Resistance - The equivalent resistance of an entire circuit.
Transformer Efficiency - The ration of output power to input power generally expressed as a percentage.
Transformer Step Down - A transformer so constructed that the number of turns in the secondary winding is less
the number of turns in the primary winding. This construction will provide less
voltage in the secondary circuit than in the primary circuit.
Transformer Step Up - A transformer so constructed that the number of turns in the secondary winding is more
than the number of turns in the primary winding. This construction will provide more
voltage in the secondary circuit than in the primary.
Transmission Lines - Any conductor or system of conductors used to carry electrical energy from its source to
a load.
Transistor - A semi-conductor device with three or more elements.
Triac - A three terminal device that is similar to two SCR’s back to back with a common gate and common
terminals. Although similar in construction and operation to the SCR, the triac controls and conducts
current flow during both alterations of an AC cycle.
Trivalent Impurity - Acceptor impurities containing only three valence electrons.
True Power - The power dissipated in the resistance of the circuit or the power actually used in the circuit.
10-13
Tunnel Diode - A heavily doped semi-conductor device which has high gain and fast switching capabilities.
Turn - One complete loop of a conductor about a core.
Turns Ratio - The ratio of number of turns in the primary winding to the number of turns in the secondary
winding of a transformer.
Unijunction Transistor - A three terminal solid state device that resembles a transistor, but is stable over a wide
range of temperatures and allows a reduction of components when used in place of a
transistor. Used in switching circuits oscillators and wave shaping circuits.
Universal Time Constant - A chart used to find the time constant of a circuit if the impressed voltage and the
value of R and C or R and L are known.
Valence - The measure of the extent to which an atom is able to combine directly with other atoms. It is
thought to depend on the number and arrangement of the electrons in the outermost shell of the
atom.
Valence Shell - The electrons that form the outermost shell of an atom.
VAR - Abbreviation for volt-amperes reactive.
Varactor - A diode that behaves like a variable capacitor with the PN junction functioning like the dielectric
and the plates of a common capacitor.
Variable Resistor - A wire wound or composition resistor the value of which may be changed.
Vector - A line used to represent both direction and magnitude.
Virtual Ground - A point in a circuit which is at ground potential, but is not connected to ground.
Volt - The unit of electromotive force of electrical pressure. One volt is the pressure required to send one
ampere of current through a resistance of one ohm.
Voltage - The term used to signify electrical pressure. Voltage is a force which causes current to flow through
an electrical conductor. The voltage of a circuit is the greatest effective difference of potential
between any two conductors of the circuit.
Voltage Amplifier - An amplifier in which the output signal voltage is greater than the input signal voltage.
Voltage Divider - A series circuit in which desired portions of the source voltage may be tapped off for use in
equipment.
Voltage Drop - The difference in voltage between two points. It is the result of the loss of electrical pressure
as a current flows through a resistance.
Voltmeter - An instrument designed to measure a difference in electrical potential in volts.
Watt - The practical unit of electrical power. It is the amount of power used when one ampere of DC flows
through a resistance of one ohm.
Wattage Rating - A rating expressing the maximum power that a device can safely handle.
Watt-Hour - A practical unit of electrical energy equal to one watt of power for one hour.
Wattmeter - An instrument for measuring electrical power in watts.
10-14
Windings - The coils found in electric motors and generators.
Wire - A solid or stranded group of solid cylindrical conductors having low resistance to current flow with any
associated insulation.
Work - The product of force and motion.
Zener Diode - A PN junction diode designed to operate in the reverse bias breakdown region.
Zener Effect - A reverse breakdown effect in diodes in which breakdown occurs at reverse voltages below 5
volts. The presence of a high energy field at the junction of a semi-conductor produces the
breakdown.
10-15