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ac  See alternating current.
AC beta  The ratio of ac collector current, ic, to ac base current, ib, or β = (ic / ib).
AC Effective Resistance, Re  The resistance of a coil for higher frequency alternating current. The value of Re is more than the dc resistance of the coil because it includes the losses associated with high frequency alternating current in a coil. These losses include skin effect, eddy currents and hysteresis losses.
AC equivalent circuit  A circuit as it appears to an ac signal. In an ac equivalent circuit all capacitors and voltage sources appear as shorts.
AC load line  A graph that shows all of the possible values of IC and VCE when a transistor amplifier is driven by an ac signal.
AC load power, PL  The ac power that is dissipated by the load, RL.
AC resistance of a diode  The equivalent resistance of a forward-biased diode as it appears to small ac signals. For a standard diode, rac = 25mV / Id. For the emitter diode in a transistor, r'e = 25mV / IE.
active component  One that can control voltage or current. Examples are transistors and diodes.
active filter A  filter that uses components or devices that have the ability to amplify such as transistors and op-amps.
active region  The region of operation where the collector of a transistor acts like a current source.acute angle Less than 90°.
A/D converter  A device that converts analog input signals to digital output.
admittance (Y)  Reciprocal of impedance Z in ac circuits. Y = 1/Z.
air gap  Air space between poles of a magnet.
alkaline cell or battery  One that uses alkaline electrolyte.
alternating current (ac)  Current that reverses direction at a regular rate. Alternating voltage reverses in polarity. The rate of reversals is the frequency.
alternation  One-half cycle of revolution of a conductor loop rotating through a magnetic field. This corresponds to one-half cycle of alternating voltage or current.
alternator  AC generator.
amp-clamp Probe  A meter which can measure ac currents, generally from the 60 Hz ac power line, without breaking open the circuit. The probe of the meter is actually a clamp which fits around the current-carrying conductor.
ampere  the basic unit of current. 1A = (1C / 1s) or 1A = (1V / 1Ω)
ampere-hour (A-H) rating  A common rating for batteries which indicates how much load current a battery can supply over a specified discharge time. For example, a battery with a 100A-H rating can deliver 1A for 100h or 2A for 50h, 4A for 25h, etc.
ampere-turn (A-t)  Unit of magnetizing force equal to 1 A x 1 turn.
ampere turns/meter (A • t / m)  The SI unit of field intensity, H.
analog multimeter  A test instrument which is used to make voltage, current and resistance measurements. An analog multimeter uses a moving pointer and a printed scale to display the value of the measured quantity.
antiresonance  Term sometimes used for parallel resonance.
apparent power  The product of voltage and current VA when V and I are out of phase.
arctangent (arctan)  An inverse trigonometric function which specifies the angle, θ, corresponding to a given tangent (tan) value.
armature  The part of a generator in which the voltage is produced. In a motor, it is commonly the rotating member. Also, the movable part of a relay.
asymmetrical JFET  A JFET that has its gate regions offset from the center of the channel. With an asymmetrical JFET the drain and source leads cannot be interchanged.
atom  the smallest particle of an element that still has the same characteristics as the element.
atomic number  the number of protons, balanced by an equal number of electrons, in an atom.
attenuation  A term which refers to a reduction in signal amplitude.
audio frequency (af)  Within the range of hearing, approximately 16 to 16,000 Hz.
autotransformer  A single, tapped winding used to step up or step down voltage.
avalanche  The effect that causes a sharp increase in reverse current, IR, when the reverse-bias voltage across a diode becomes excessive.
average value  In sine-wave ac voltage or current, 0.637 of peak value.
B-H magnetization curve  A graph of field intensity H versus flux density B.
back-off ohmmeter scale  Ohmmeter readings from right to left.
balanced bridge  A circuit consisting of two series strings in parallel. The balanced condition occurs when the voltage ratio in each series string is identical. The output from the bridge it taken between the centers of each series string. When the voltage ratios in each series string are identical, the output voltage is zero and the bridge circuit is said to be balanced.
bandpass filter  Filter that allow coupling a band of frequencies to the load.
bandstop filter  Filter that prevents a band of frequencies from being coupled to the load.
bandwidth  A range of frequencies that has a resonant effect in LC circuits.
bank  Components connected in parallel.
barrier potential, VB  The potential difference at the pn junction of a diode. VB exists between the wall of positive and negative ions which are created as a result of free electrons diffusing from the n-side of the diode to the p-side.
base  A thin and very lightly doped region in a transistor. The base is sandwiched between the emitter and collector regions.
battery  Group of cells connected in series or parallel.
bias  A control voltage or current.
bidirectional diode thyristor  Another name for a diac.
bilateral components  Electronic components which have the same current for opposite polarities of applied voltage.
bleeder current  Steady current from source used to stabilize output voltage with changes in load current.
branch  Part of a parallel circuit.
breakdown region  The region of transistor operation where a large undesired collector current flows as a result of the collector-base diode breaking down due to excessive reverse-bias voltage.
breakdown voltage, VBR  The reverse bias voltage at which the avalanche effect occurs. The avalanche effect causes the reverse current, IR, to increase sharply.
brushes  In a motor or generator, devices that provide stationary connections to the rotor.
bulk resistance, rB  The resistance of the p and n materials in a diode.
bypass capacitor  One that has very low reactance in a parallel path.
C  Symbol for capacitance. Abbreviation for coulomb, the unit of electric charge.
calorie  Amount of heat energy needed to raise the temperature of one gram of water by 1°C.
capacitance  The ability to store electric charge.
capacitive reactance, xC  capacitive reactance, xC A measure of a capacitors opposition to the flow of alternating current. xC is measured in ohms. xC = 1 / 2πfC or xC = VC / IC. xC applies only to sine wave ac circuits.
capacitive voltage divider  A voltage divider which consists of series-connected capacitors. The amount of voltage across each capacitor is inversely proportional to its capacitance value.
capacitor  Device used to store electric charge.
carbon-composition resistors  Resistors made of finely divided carbon or graphite mixed with a powdered insulating material.
carbon-film resistors  Resistors made by depositing a thin layer of carbon on an insulated substrate. The carbon film is cut in the form of a spiral.
Celsius scale (°C)  Temperature scale that uses 0° for the freezing point of water and 100° for the boiling point. Formerly called centigrade.
ceramic  Insulator with a high dielectric constant.
cgs  Centimeter-gram-second system of units.
channel  The area or conducting region between the drain and source terminals of an FET. The channel can be made of either n-type or p-type semiconductor material.
charging  The effect of increasing the amount of charge stored in a capacitor. The accumulation of stored charge results in a buildup of voltage across the capacitor.
charging  The process of reversing the current, and thus the chemical action, in a cell or battery to re-form the electrodes.
chassis ground  Common return for all electronic circuits mounted on one metal chassis or PC board. Usually connects to one side of dc supply voltage.
chip capacitor  A surface-mounted capacitor.
choke  Inductance with high xL compared with the R of the circuit.
circuit  a path for current flow.
circuit breaker  A protective device that opens when excessive current flows in circuit. Can be reset.
circular mil (c mil)  Cross-sectional area of round wire with diameter of 1 mil or 0.001 in.
Class A amplifier  An amplifier in which the collector current, IC, flows for the full 360° of the ac input cycle.
Class B amplifier  An amplifier in which the collector current, IC, flows for only 180° of the ac input cycle.
Class B push-pull amplifier  A Class B amplifier that uses two transistors to reproduce the full ac cycle of input votlage. Each transistor conducts on opposite half-cycles of the input voltage.
Class C amplifier  An amplifier in which the collector current, IC, flows for 120° or less of the ac input cycle.
closed loop cutoff frequency, fCL  The frequency at which the closed loop voltage gain decreases to 70.7% of its maximum value.
closed loop voltage gain, ACL  The voltage gain of an amplifier with negative feedback.
coaxial cable  An inner conductor surrounded by an outer conductor that serves as a shield.
coding of capacitors  The method used to indicate the value of a capacitor.
Coefficient of Coupling, k  The fraction of total flux from one coil linking another coil nearby.
coil  Turns of wire conductor to concentrate a magnetic field.
collector  A large, moderately doped region in a transistor. The collector is the largest of all three transistor regions because it dissipates the most heat.
color code  System in which colors are used to indicate values in resistors.
common mode input  An identical input voltage appearing on both inputs of a differential amplifier.
common mode rejection ratio (CMRR)  The ratio of differential voltage gain, Ad, to common mode voltage gain, Acm. CMRR is usually specified in decibels.
common mode voltage gain, Acm  The voltage gain of a differential amplifier for a common mode signal.
common-base amplifier  A transistor amplifier that has its input applied to the emitter and its output taken from the collector. The common-base amplifier provides a high voltage and power gain but its current gain is less than 1.
common-collector amplifier  A transistor amplifier that has its input applied to the base and its output taken from the emitter. The common-collector amplifier provides a high current and power gain but its voltage gain is less than 1.
common-drain amplifier  An amplifier that has its input applied to the gate and its output taken from the source. Another name for the common-drain amplifier is the source follower.
common-emitter amplifier  A transistor amplifier that has its input applied to the base and its output taken from the collector. The common-emitter amplifier provides a high voltage and current gain and a very high power gain.
common-gate amplifier  An amplifier that has its input applied to the source and its output taken from the drain.
common-source amplifier  An amplifier that has its input applied to the gate and its output taken from the drain.
commutator  Converts reversing polarities to one polarity.
comparator  An op-amp circuit that compares the signal voltage on one input with a reference voltage on the other.
complex number  Has real and j terms; uses form A + jB.
compound  A combination of two or more elements.
condenser  Another (older) name for a capacitor.
conductance (G)  Ability to conduct current. It is the reciprocal of resistance, G = 1/R. The unit is the siemens (S).
conductor  Any material that allows the free movement of electric charges, such as electrons, to provide an electric current.
constant-current source  A generator whose internal resistance is very high compared with the load resistance. Because its internal resistance is so high, it can supply a constant current to a load whose resistance value varies over a wide range.
Constant-Voltage Source  A generator whose internal resistance is very low compared with the load resistance. Because its internal resistance is so low, it can supply a constant voltage to a load whose resistance value varies over a wide range.
continuity  Continuous path for current. Reading of zero ohms with an ohmmeter.
conventional current  the direction of current flow associated with positive charges in motion. The current flow direction is from a positive to a negative potential, which is in the opposite direction of electron flow.
corona  Effect of ionization of air around a point at high potential.
cosine  A trigonometric function of an angle, equal to the ratio of the adjacent side to the hypotenuse in a right triangle.
cosine wave  One whose amplitudes vary as the cosine function of an angle. It is 90° out of phase with the sine wave.
coulomb (C)  Unit of electric charge. 1 C = 6.25 x 1018 electrons.
counter emf (cemf)  A term used to describe the effect of an induced voltage in opposing a change in current.
coupling capacitor  Has very low xC in series path.
covalent bond  Pairing of atoms with electron valence of ±4.
covalent bonding  The sharing of valence electrons between neighboring atoms in a silicon crystal or other crystalline structure.
cps  Cycles per second. Formerly used as unit of frequency. Replaced by hertz (Hz) unit, where 1 Hz = 1 cps.
crossover distortion  The distortion that occurs in a Class B push-pull amplifier when the transistors are biased right at cutoff. When the input voltage crosses through zero both transistors in the push- pull amplifier are off and the output voltage cannot follow the input voltage.
CRT  Cathode-ray tube. A device that converts electric signals to a visual display on a fluorescent screen.
crystal filter  A filter which is made up of a crystalline material such as quartz. Crystal filters are often used in place of conventional LC circuits because there Q is so much higher.
Curie Temperature  The temperature at which a magnetic material loses its ferromagnetic properties.
current  A movement of electric charges around a closed path or circuit.
current divider  A parallel circuit to provide branch I less than the main-line current.
current gain, Ai  The ratio of output current to input current in a transistor amplifier.
current source  Supplies I = V/ri to load with ri in parallel.
current-source region  The region of operation in which the drain of a JFET acts as a current source. The current-source region of operation exists when VDS > VP.
cutoff  The region of transistor operation where the collector current, IC, is zero.
Cutoff Frequency  The frequency at which the attenuation of a filter reduces the output amplitude to 70.7% of its value in the passband.
cycle  One complete set of values for a repetitive waveform.
damping  Reducing the Q of a resonant circuit to increase the bandwidth.
D'Arsonval meter  A dc analog meter movement commonly used in ammeters and voltmeters.
dB  Abbreviation for decibel. Equals 10 times the logarithm of the ratio of two power levels.
DC alpha, αdc  The ratio of collector current, IC, to emitter current, IE, in a transistor; αdc = (IC / IE).
DC beta, βdc  The ratio of collector current, IC, to base current, IB, in a transistor; βdc = (IC / IB).
DC input power, PCC  The amount of dc power dissipated by a transistor amplifier.
DC load line  A graph which shows all of the possible values of IC and VCE for a given transistor amplifier. The end-points of the dc load line are IC(sat) and VCE(off) which represent the values of IC and VCE when the transistor is in saturation and cutoff.
dc  See direct current.
decade  A 10:1 range of values.
decade resistance box  A unit for providing any resistance within a wide range of values.
decibel  See dB.
decimal notation  Numbers that are written in standard form without using powers of 10 notation.
degaussing  Demagnetizing by applying an ac field and gradually reducing it to zero.
delta (Δ) network  Three components connected in series in a closed loop. Same as pi (π) network.
depletion mode  The mode of operation for a MOSFET in which the polarity of VGS causes the drain current to be reduced as the channel becomes depleted of available charge carriers.
depletion zone  The area located at the pn junction of a diode which is void or depleted of all charge carriers.
derating curve  A graph showing how the power rating of a resistor decreases as its operating temperature increases.
derating factor  The amount that the power rating of a transistor must be reduced for each degree Celsius above 25°C. The derating factor is specified in W/°C.
DIAC  A bidirectional semiconductor device that conducts when the voltage across its terminals reaches the breakover voltage ±VBO. Once conducting the voltage across the diac drops to a very low value.
diamagnetic  Material that can be weakly magnetized in the direction opposite from the magnetizing field.
dielectric absorption  The inability of a capacitor to completely discharge to zero. Dielectric absorption is sometimes called battery action or capacitor memory.
dielectric constant  Ability to concentrate the electric field in a dielectric.
dielectric material  Insulating material. It cannot conduct current but does store charge.
dielectric strength  The ability of a dielectric to withstand a potential difference without internal arcing.
differential input voltage, Vid  The voltage difference between the two inputs applied to a differential amplifier.
differential voltage gain, Ad  The ratio of output voltage, Vout, to differential input voltage, Vid.
differentiator  An RC circuit with a short time constant for pulses across R.
diode  A unidirectional device that allows current to flow through it in only one direction.
diode bias  A form of biasing for Class B push-pull amplifiers which uses diodes to provide a slight amount of forward-bias for the base-emitter junctions of each transistor.
direct current (dc)  Current that flows in only one direction. DC voltage has a steady polarity that does not reverse.
discharging  The action of neutralizing the charge stored in a capacitor by connecting a conducting path across the capacitor leads.
discharging  The process of neutralizing the separated charges on the electrodes of a cell or battery as a result of supplying current to a load resistance.
DMM  Digital multimeter. A piece of test equipment used to measure voltage, current, and resistance in an electronic circuit.
doping  The process of adding impurity atoms to a pure semiconductor material such as silicon.
Double Subscript Notation  A notational system which identifies the points in the circuit where a voltage measurement is to be taken, i.e.; VAG. The first letter in the subscript indicates the point in the circuit where the measurement is to be taken whereas the second letter indicates the point of reference.
DPDT  Double-pole double-throw switch or relay contacts.
DPST  Double-pole single-throw switch or relay contacts.
drain  One of the three leads of an FET. The drain lead connects to one end of the conducting channel.
dynamometer  Type of ac meter, generally for 60 Hz.
earth ground  A direct connection to the earth usually made by driving copper rods into the earth and then connecting the ground wire of an electrical system to this point. The earth ground connection can serve as a common return path for the current in a circuit. The symbol for earth ground is.
eddy current  Circulating current induced in the iron core of an inductor by ac variations of magnetic flux.
effective value  For sine-wave ac waveform, 0.707 of peak value. Corresponds to heating effect of same dc value. Also called rms value.
efficiency  Ratio of power out put to power input 100%.
EIA  Electronic Industries Alliance.
electric field  The invisible lines of force between opposite electric charges.
electricity  Dynamic electricity is the effect of voltage in producing current in conductors. Static electricity is accumulation of charge.
electrolyte  Solution that forms ion charges.
electrolytic capacitor  Type with very high C because electrolyte is used to form very thin dielectric. Must be connected with correct polarity in a circuit.
electromagnet  Magnet whose magnetic field is associated with electric current in a coil.
electron  Basic particle of negative charge in orbital rings around the nucleus in an atom.
electron flow  Current of negative charges in motion. Direction is from the negative terminal of the voltage source, through the external circuit, and returning to the positive side of the source. Opposite to the direction of conventional current.
electron-hole pair  The creation of a free electron and a hole when a valence electron gains enough energy to leave its covalent bond in a silicon crystal.
Electron  Valence the number of electrons in an incomplete outermost shell of an atom.
electron volt  Unit of energy equal to the work done in moving a charge of 1 electron through a potential difference of 1 V.
Element  a substance that cannot be decomposed any further by chemical action.
emf  Electromotive force; voltage that produces current in a circuit.
emitter  The most heavily doped region in a transistor. Its job is to inject or emit current carriers into the base region.
emitter bypass capacitor, CE  A capacitor that bypasses the ac signal around the emitter resistor in a transistor amplifier.
emitter follower  Another name for the common-collector amplifier.
engineering notation  A form of powers of 10 notation in which a number is expressed as a number between 1 and 1000 times a power of 10 that is a multiple of 3.
enhancement mode  The mode of operation for a MOSFET in which the polarity of VGS causes the conductivity of the channel to be enhanced, thus increasing the drain current.
equivalent resistance, REQ  In a parallel circuit this refers to a single resistance that would draw the same amount of current as all of the parallel connected branches.
equivalent series resistance (ESR)  A resistance in series with an ideal capacitor which collectively represents all of the losses in a capacitor. Ideally, the ESR of a capacitor should be zero.
extrinsic semiconductor  A semiconductor that has been doped with impurity atoms to alter the characteristics of the material, mainly its conductivity.
F connector  Solderless plug for coaxial cable.
funity  The frequency where the open-loop voltage gain, Avol, of an op-amp equals 1 or unity.
Fahrenheit scale (°F)  Temperature scale that uses 32° for the freezing point of water and 212° for the boiling point.
farad (F)  Unit of capacitance. Value of one farad stores one coulomb of charge with one volt applied.
Faraday's law  or magnetic induction, the generated voltage is proportional to the flux and its rate of change.
ferrite  Magnetic material that is not a metal conductor.
Ferrite Core  A type of core which has a high value of flux density, like iron, but is an insulator. A ferrite core used in a coil has minimum eddy current losses due to its high resistance.
ferromagnetic  Magnetic properties of iron and other metals that can be strongly magnetized in the same direction as the magnetizing field.
field  Group of lines of force; magnetic or electric field.
field effect transistor (FET)  A unipolar device which relies on only one type of charge carrier, either electrons or holes. FET's are voltage controlled devices with an input voltage controlling the output current.
field intensity (H)  The mmf per unit of length.
field winding  The part of a motor or generator that supplies the magnetic field cut by the armature.
film capacitor  A capacitor that uses a plastic film for its dielectric.
filter  Circuit that separates different frequencies.
Float Charging  A method of charging in which the charger and the battery are always connected to each other for supplying current to the load. With this method, the charger provides the current for the load and the current necessary to keep the battery fully charged.
fluctuating direct current  Varying voltage and current but no change in polarity.
flux (φ)  Magnetic lines of force.
flux density (π)  Amount of flux per unit area.
flywheel effect  Ability of an LC circuit to continue oscillating after the energy source has been removed.
Form Factor  The ratio of the rms to average rms values. For a sine wave, rms/avg = 1.11.
forward blocking current  The small current that flows in an SCR before breakover is reached.
forward breakover voltage, VBRF  The forward voltage across an SCR at which the SCR begins to conduct. The value of VBRF is controlled by the amount of gate current, IG.
forward-bias  The polarity of voltage across a diode which permits current to flow through it easily.
free electron  electron that can move freely from one atom to the next.
frequency (f)  Number of cycles per second for a waveform with periodic variations. The unit is hertz (Hz).
frequency multiplier  A tuned Class C amplifier that has its LC tank circuit tuned to a harmonic or multiple of the input frequency.
fuel cell  An electrochemical device which converts the chemicals hydrogen and oxygen into water, and in the process produces electricity. A fuel cell provides a steady dc output voltage that can power motors, lights or other appliances. Unlike a regular battery, however, a fuel cell constantly has chemicals flowing into it so it never goes dead.
full-wave rectifier  A circuit that provides an entirely positive or negative output voltage when an ac input voltage is applied. A full-wave rectifier provides an output for both the positive and negative alternations of the input voltage.
fuse  Metal link that melts from excessive current and opens a circuit.
galvanic cell  Electrochemical type of voltage source.
galvanometer  Measures electric charge or current.
Ganged Capacitors  Two or three capacitor sections on one common shaft which can be rotated.
gate  One of the three leads of an FET. The gate is used to control the drain current.
gate-source cutoff voltage, VGS(off)  The amount of gate-source voltage required to reduce the drain current, ID, to zero.
gauss (G)  Unit of flux density in cgs system equal to one magnetic line of force per square centimeter.
generator  A device that produces voltage output. Is a source for either dc or ac V and I.
germanium (Ge)  Semiconductor element used for transistors and diodes.
giga (G)  Metric prefix for 109.
gilbert (Gb)  Unit of magnetomotive force in cgs system. One gilbert equals 0.794 ampere-turn.
graph cycle  A 10:1 range of values on logarithmic graph paper.
ground  Common return to earth for ac power lines. Chassis ground in electronic equipment is the common return to one side of the internal power supply.
half-power points  Bandwidth defined with 70.7% response for resonant LC circuit.
half-wave rectifier  A circuit that provides an entirely positive or negative output voltage when an ac input voltage is applied. A half-wave rectifier provides an output for either the positive or negative alternation of the input voltage but not both.
hall effect  Small voltage generated by a conductor with current in an external magnetic field.
harmonic  Exact multiple of fundamental frequency.
henry (H)  Unit of inductance. Current change of one ampere per second induces one volt across an inductance of one henry.
hertz (Hz)  Unit of frequency. One hertz equals one cycle per second.
High-Pass Filter  A filter that allows the higher frequency components of the applied voltage to develop appreciable output voltage while at the same time attenuating or eliminating the lower frequency components.
holding current, IH  The minimum amount of current required to hold a thyristor (diac, SCR or triac) in its conducting state.
holding current  The minimum amount of current required to keep a relay energized.
hole  The absence of a valence electron in a covalent bond structure. The hole exhibits a positive charge.
hole current  Motion of hole charges. Direction is the same as that of conventional current, opposite from electron flow.
horsepower (hp)  A unit of mechanical power corresponding to 550 ft. lbs/s. In terms of electric power, 1 hp 746 W.
hot resistance  The R of a component with its normal load current. Determined by V/I.
hot-wire meter  Type of ac meter.
hydrometer  A device used to check the state of charge of a cell within a lead-acid battery.
hypotenuse  Side of a right triangle opposite the 90° angle.
hysteresis  In electromagnets, the effect of magnetic induction lagging in time behind the applied magnetizing force.
Hz  See hertz.
IGFET  Insulated gate field effect transistor. Another name for a MOSFET.
imaginary number  Value at 90°, indicated by j operator, as in the form jA.
impedance matching  Occurs when a transformer is used for its impedance transformation properties. With impedance matching, maximum power is delivered to the load, RL.
impedance, Z  The total opposition to the flow of current in a sine wave ac circuit. In an RC circuit, the impedance, Z, takes into account the 90° phase relation between xC and R. Impedance, Z, is measured in ohms.
inductance (L)  Ability to produce induced voltage when cut by magnetic flux. Unit of inductance is the henry (H).
induction  Ability to generate V or I without physical contact. Electromagnetic induction by magnetic field; electrostatic induction by electric field.
Inductive Reactance, xL  A measure of an inductor's opposition to the flow of alternating current. xL is measured in ohms and is calculated as xL = 2πfL or xL = VL / IL.
inductor  Coil of wire with inductance.
input bias current, IB  The average of the two op-amp input currents IB+ and IB-.
input impedance, Zin  The impedance of the input of an amplifier as seen by the ac signal source driving the amplifier.
input offset current, Ios  The difference between two op-amp input currents IB+ and IB-.
insulator  A material that does not allow current to flow when voltage is applied, because of its high resistance.
integrator  An RC circuit with a long time constant. Voltage output across C.
interbase resistance, RBB  The resistance of the n-type silicon bar in a UJT. RBB appears as two resistances, RB1 and RB2. RBB = RB1 + RB2.
internal resistance ri  Limits the current supplied by the voltage source to I = V/ri.
intrinsic semiconductor  A semiconductor material with only one type of atom.
intrinsic standoff ratio, η  The ratio of RB1 or RB1 or η = RB1 / RB1 + RB2.
inverse relation  Same as reciprocal relation. As one variable increases, the other decreases.
Inversely Proportional  The same as a reciprocal relation; as the value in the denominator increases the resultant quotient decreases. In the formula xC = 1 / 2πƒC, xC is inversely proportional to both f and C. This means that as f and C increase, xC decreases.
ion  Atom or group of atoms with net charge. Can be produced in liquids, gases, and doped semiconductors.
Ionization Current  A current which results from the movement of ion charges in a liquid or gas.
IR  drop Voltage across a resistor.
iron-vane meter  Type of ac meter, generally for 60 Hz.
j operator  Indicate 90° phase angle, as n j8Ω for xL. Also. -j8Ω is at 90§ for xC.
JFET  Junction Field Effect Transistor
joule (J)  Practical unit of work or energy. One joule equals one watt-second of work.
k  Coefficient of coupling between coils.
keeper  Magnetic material placed across the poles of a magnet to form a complete magnetic circuit. Used to maintain strength of magnetic field.
Kelvin (K) scale  Absolute temperature scale, 273° below values on Celsius scale.
kilo (k  Metric prefix for 103.
Kilowatthour  A large unit of electrical energy corresponding to 1 kW · 1h.
Kirchhoff's current law (KCL)  The sum of all currents into and out of any branch point in a circuit must equal zero.
Kirchhoff's voltage law (KVL)  The sum of all voltages around any closed path must equal zero.
laminations  Thin sheets of steel insulated from one another to reduce eddy-current losses in inductors, motors, etc.
Leakage Current  The current that flows through the dielectric of a capacitor when voltage is applied across the capacitor plates.
leakage current  The very small current that flows when a diode is reverse-biased. The leakage current is mainly due to the thermally-generated minority carriers that exist in both sections of the diode.
leakage flux  Any magnetic field lines that do not link two coils which are in close proximity to each other.
leakage resistance  A resistance in parallel with a capacitor which represents all of the leakage paths through which a capacitor can discharge.
Leclanché cell  Carbon-zinc primary cell.
left hand rule  If the coil is grasped with the fingers of the left hand curled around the coil in the direction of electron flow, the thumb points to the North pole of the coil.
Lenz's law  Induced current has magnetic field that opposes the change causing the induction.
light-emitting diode (LED)  A diode that emits a certain color light when forward-biased. The color of light emitted by the diode is determined by the type of material used in the doping process.
linear amplifier  Any amplifier that produces an output signal that is an exact replica of the input signal.
linear component  An electronic component whose current is proportional to the applied voltage.
linear proportion  Straight-line graph between two variables. As one increases, the other increases in direct proportion.
linear resistance  A resistance with a constant value of ohms.
load  Takes current from the voltage source, resulting in load current.
load currents  The currents drawn by the electronic devices and/or components connected as loads in a loaded voltage divider.
loaded voltage  The voltage at a point in a series voltage divider where a parallel load has been connected.
loading effect  Source voltage is decreased as amount of load current increases.
long-time constant  A long-time constant can arbitrarily be defined as one that is five or more times longer than the pulse width of the applied voltage.
loop  Any closed path in a circuit.
loop equation  An equation which specifies the voltages around a loop.
low-pass filter  A filter that allows the lower frequency components of the applied voltage to develop appreciable output voltage while at the same time attenuating or eliminating the higher frequency components.
magnetic flux (Φ)  Another name used to describe magnetic field lines.
magnetic pole  Concentrated point of magnetic flux.
magnetism  Effects of attraction and repulsion by iron and similar materials without the need for an external force. Electromagnetism includes the effects of a magnetic field associated with an electric current.
magnetomotive force (mmf)  Ability to produce magnetic lines of force. Measured in units of ampere-turns.
magnitude  Value of a quantity regardless of phase angle.
main line  The pair of leads connecting all of the individual branches in a parallel circuit to the terminals of the applied voltage, VA. The main line carries the total current, IT, flowing to and from the terminals of the voltage source.
majority current carrier  The dominate type of charge carrier in a doped semiconductor material. In an n-type semiconductor free electrons are the majority current carriers whereas in a p-type semiconductor holes are the majority current carriers.
make and break  Occurs when contacts close and open.
maximum working voltage rating  The maximum allowable voltage a resistor can safely withstand without internal arcing.
maxwell (Mx)  Unit of magnetic flux equal to one line of force in the magnetic field.
mega (M)  Metric prefix for 106.
mesh current  Assumed current in a closed path, without any current division, for application of Kirchhoff's current law.
mesh  The simplest possible closed path within a circuit.
metal-film resistors  Resistors made by spraying a thin film of metal onto a ceramic substrate. The metal film is cut in the form of a spiral.
metric prefixes  Letter symbols used to replace the powers of 10 that are multiples of 3.
micro (μ)  Metric prefix for 10-6.
microfarad  A small unit of capacitance equal to 1 x 10-6F.
midpoint bias  A bias point that is centered between cutoff and saturation on the dc load line.
milli (m)  Metric prefix for 10-3.
Millman's theorem  A theorem which provides a short-cut for finding the common voltage across any number of parallel branches with different voltage sources.
minority current carrier  The type of charge carrier that appears sparsely throughout a doped semiconductor material. In an n-type semiconductor, holes are the minority current carriers whereas free electrons are the minority current carriers in a p-type semiconductor.
mks  Meter-kilogram-second system of units.
molecules  the smallest unit of a compound with the same chemical characteristics.
motor  A device that produces mechanical motion from electric energy.
MOSFET  Metal Oxide Semiconductor Field Effect Transistor
motor action  A motion that results from the net force of two magnetic fields that can aid or cancel each other. The direction of the resultant force is always from a stronger field to a weaker field.
multiplier resistor  Resistor in series with a meter movement for voltage ranges.
mutual induction (LM)  Ability of one coil to induce voltage in another coil.
nano (n)  Metric prefix for 10-9.
nanofarad  A small unit of capacitance equal to 1 x 10-9F.
NC  Normally closed for relay contacts, or no connection for pinout diagrams.
negative feedback  A form of amplifier feedback where the returning signal has a phase that opposes the input signal.
negative saturation voltage, -Vsat  The lower limit of output voltage for an opamp.
negative temperature coefficient (NTC)  A characteristic of a thermistor indicating that its resistance decreases with an increase in operating temperature.
neutron  Particle without electric charge in the nucleus of an atom.
node  A common connection for two or more branch currents.
nonlinear resistance  A resistance whose value changes as a result of current producing power dissipation and heat in the resistance.
nonsinusoidal waveform  Any waveform that is not a sine or a cosine wave.
Norton's theorem  Method of reducing a complicated network to one current source with shunt resistance.
n-type semiconductor  A semiconductor that has been doped with pentavalent impurity atoms. The result is a large number of free electrons throughout the material. Since the electron is the basic particle of negative charge, the material is called n-type semiconductor material.
nucleus  the massive, stable part of the atom which contains both protons and neutrons.
obtuse angle  More than 90°.
octave  A 2 : 1 range of values.
oersted (Oe)  Unit of magnetic field intensity; 1 Oe = 1 Gb/cm.
ohm (Ω)  Unit of resistance. Value of one ohm allows current of one ampere with potential difference of one volt.
Ohm's law  In electric circuits, I = V/R.
ohmic region  The region of operation for a JFET where the drain current, ID, increases in direct proportion to VDS. The ohmic region of operation exists when VDS < VP.
ohms per volt rating  Sensitivity rating for a voltmeter. High rating means less meter loading.
open circuit  One that has infinitely high resistance, resulting in zero current.
open-circuit voltage  The voltage present across the output terminals of a voltage source when no load is present.
open-loop cutoff frequency, fOL  The frequency at which the open loop voltage gain of an op-amp is down to 70.7% of its maximum value at dc.
open-loop voltage gain, AVOL  The voltage gain of an op-amp without negative feedback.
operational amplifier (op-amp)  A high-gain, direct coupled differential amplifier.
oscilloscope  A piece of test equipment used to view and measure a variety of different ac waveforms.
output impedance, Zout  The impedance at the output of an amplifier as seen by the load being driven by the amplifier.
parallel circuit  One that has two or more branches for separate currents from one voltage source.
paramagnetic  Material that can be weakly magnetized in the same direction from the magnetizing force.
passive component  Components such as resistors, capacitors, and inductors. They do not generate voltage or control current.
PC board  A device that has printed circuits.
peak inverse voltage (PIV)  The maximum instantaneous reverse-bias voltage across a diode.
peak reverse voltage rating, VROM  The maximum reverse-bias voltage that can be safely applied between the anode and cathode terminals of an SCR with the gate open.
peak-to-peak value (p-p)  Amplitude between opposite peaks.
peak value  Maximum amplitude, in either polarity; 1.414 times rms value for sine-wave V or I.
pentavalent atom  An atom with 5 valence electrons.
percent efficiency  For an amplifier, this refers to the percentage of dc input power that is converted to useful ac output power.
permanent magnet (PM)  It has magnetic poles produced by internal atomic structure. No external current needed.
permeability  Ability to concentrate magnetic lines of force.
phase angle  Angle between two phasors; denotes time shift.
phasing dots  Used on transformer windings to identify those leads having the same instantaneous polarity.
phasor  A line representing magnitude and direction of a quantity, such as voltage or current, with respect to time.
phasor Triangle  A right triangle which represents the phasor sum of two quantities 90° out of phase with each other.
pickup current  The minimum amount of current required to energize a relay.
pico (p)  Metric prefix for 10-12.
picofarad  A small unit of capacitance equal to 1 x 10-12F.
pinchoff voltage, VP  The drain-source voltage at which the drain current, ID, levels off. VP is the border between the ohmic and current-source regions of operation.
polar form  Form of complex numbers that gives uoi magnitude and phase angle in the form A <0°.
polarity  Property of electric charge and voltage. Negative polarity is excess of electrons. Positive polarity means deficiency of electrons.
Pole  The number of completely isolated circuits that can be controlled by a switch.
positive saturation voltage, +Vsat  The upper limit of output voltage for an opamp.
Positive Temperature Coefficient (PTC)  A characteristic of a thermistor indicating that its resistance increases with an increase in operating temperature.
potential difference  Ability of electric charge to do work in moving another charge. Measured in volt units.
potentiometer  Variable resistor with three terminals connected as a voltage divider.
power (P)  Rate of doing work. The unit of electric power is the watt.
power amplifier  A circuit that is designed to deliver large amounts of power to a low impedance load.
power bandwidth (fmax)  The highest undistorted frequency out of an op-amp without slew-rate distortion.
power factor  Cosine of the phase angle for a sine-wave ac circuit. Value is between 1 and 0.
power gain, AP  The ratio of output power to input power in a transistor amplifier. AP can also be calculated as: AP = AV x Ai.
power supply  A piece of test equipment used to supply dc voltage and current to electronic circuits under test.
powers of 10  A numerical representation consisting of a base of 10 and an exponent; the base 10 raised to a power.
preferred values  Common values of resistors and capacitors generally available.
primary cell or battery  Type that cannot be recharged.
primary winding  Transformer coil connected to the source voltage.
principal Node  A common connection for three or more components in a circuit where currents can combine or divide.
printed wiring  Conducting paths printed on plastic board.
proportional  A mathematical term used to describe the relationship between two quantities. For example, in the formula xL = 2πfL, xL is said to be directly proportional to both the frequency, f, and the inductance, L. The term proportional means that if either f or L is doubled xL will double. Similarly, if either f or L is reduced by one-half, xL will be reduced by one-half. In other words, xL will increase or decrease in direct proportion to either f or L.
proton  Particle with positive charge in the nucleus of an atom.
p-type semiconductor  A semiconductor that has been doped with trivalent impurity atoms. The result is a large number of holes in the material. Since a hole exhibits a positive charge, the material is called p-type semiconductor material.
pulsating DC  A dc voltage or current that varies in magnitude but does not reverse in polarity or direction. Another name for pulsating dc is fluctuating dc.
pulsating dc  Includes ac component on average dc axis.
pulse  A sharp rise and decay of voltage or current of a specific peak value for a brief period of time.
Q  Figure of quality or merit, in terms of reactance compared with resistance. The Q of a coil is xL/ri. For an LC circuit, Q indicates sharpness of resonance. Also used as the symbol for charge: Q = CV.
Q of a Coil  The quality or figure of merit for a coil. More specifically, the Q of a coil can be defined as the ratio of reactive power in the inductance to the real power dissipated in the coil•s resistance. Q = xL / ri.
Q point  The values of IC and VCE that exist in a transistor amplifier with no ac signal present. quadrature phase A 90° phase angle.
R  Symbol for resistance.
radian (rad)  Angle of 57.3°. Complete circle includes 2π rad.
radio frequency (rf)  A frequency high enough to be radiated efficiently as electromagnetic waves, generally above 30 kHz. Usually much higher.
ramp  Sawtooth waveform with linear change in V or I.
ratio arm  Accurate, stable resistors in one leg of a Wheatstone bridge or bridge circuit in general. The ratio arm fraction, R1 / R2, can be varied in most cases, typically in multiples of 10. The ratio arm fraction in a Wheatstone bridge determines two things; the placement accuracy of the measurement of an unknown resistor, Rx, and the maximum unknown resistance, Rx(max), that can be measured.
RC phase-shifter  An application of a series RC circuit in which the output across either R or C provides a desired phase shift with respect to the input voltage. RC phase-shifter circuits are commonly used to control the conduction time of semiconductors in power control circuits.
reactance  Property of L and C to oppose flow of I that is varying. Symbol is xC or xL. Unit is the ohm.
real number  Any positive or negative number not containing j. (A + jB) is a complex number but A and B by themselves are real numbers.
real power  The net power consumed by resistance. Measured in watts.
reciprocal relation  Same as inverse relation. As one variable increases, the other decreases.
Reciprocal Resistance Formula  A formula which states that the equivalent resistance, REQ, of a parallel circuit equals the reciprocal of the sum of the reciprocals of the individual branch resistances.
rectangular form  Representation of a complex number in the form A + jB.
reflected impedance  The value of impedance reflected back into the primary from the secondary.
relative permeability (μr)  The ability of a material to concentrate magnetic flux. Mathematically, relative permeability, designated ur, is a ratio of the flux density (B) in a material such as iron to the flux density, B, in air. There are no units for μr because it is comparison of two flux densities and the units cancel.
relative permittivity ξr  A factor which indicates the ability of an insulator to concentrate electric flux, also known as the dielectric constant, Kξ.
relay  Automatic switch operated by current in a coil.
relay chatter  The vibrating of relay contacts.
resistance (R)  Opposition to current. Unit is the ohm (Ω).
resistance wire  A conductor having a high resistance value.
resonance  Condition of xL = xC in an LC circuit to favor the resonant frequency for a maximum in V, I, or Z.
resonant frequency  The frequency at which the inductive reactance, xL and the capacitive reactance, xC of an LC circuit are equal.
reverse-bias  The polarity of voltage across a diode which prevents the diode from conducting any current.
rheostat  Variable resistor with two terminals to vary I.
ringing  Ability of an LC circuit to oscillate after a sharp change in V or I.
root-mean-square (rms)value  For sine-wave ac waveform, 0.707 of peak value. Also called effective value.
rotor  Rotating part of generator or motor.
saturation  The region of transistor operation where the collector current no longer increases with further increases in base current.
saturation region  The region to the right of the valley point, on the characteristic curve of a UJT.
sawtooth wave  One in which amplitude values have a slow linear rise or fall and a sharp change back to the starting value. Same as a linear ramp.
Schmitt trigger  An op-amp comparator that utilizes positive feedback.
scientific notation  A form of powers of 10 notation in which a number is expressed as a number between 1 and 10 times a power of 10.
secondary cell or battery  Type that can be recharged.
secondary winding  Transformer coil connected to the load.
self-inductance (L)  Inductance produced in a coil by current in the coil itself.
semiconductor  a material which is neither a good conductor nor a good insulator.
series-aiding  A connection of coils in which the coil current produces the same direction of magnetic field for both coils.
series-aiding voltages  Voltage sources which are connected so that the polarities of the individual sources aid each other in producing current in the same direction in the circuit.
series circuit  One that has only one path for current.
series components  Components which are connected in the same current path.
series opposing  A connection of coils in which the coil current produces opposing magnetic fields for each coil.
series-opposing voltages  Voltage sources which are connected so that the polarities of the individual sources will oppose each other in producing current flow in the circuit.
series string  A combination of series resistances.
shield  Metal enclosure preventing interference from radio waves.
short circuit  Has zero resistance, resulting in excessive current.
short-time constant  A short-time constant can arbitrarily be defined as one that is one-fifth or less the time of the pulse width of the applied voltage.
shunt resistor  A parallel connection. A device to increase the range of an ammeter.
SI  Abbreviation for Système International, a system of practical units based on the meter, kilogram, second, ampere, kelvin, mole, and candela.
siemen (S)  Unit of conductance. Reciprocal of ohms unit.
silicon (Si)  Semiconductor element used for transistors, diodes, and integrated circuits.
silicon controlled rectifier (SCR)  A unidirectional semiconductor device, like a diode, that remains in a nonconducting state, although forward-biased, until the forward breakover voltage is reached. Once conducting, the voltage across the SCR drops to a very low value.
sine  Trigonometric function of an angle, equal to the ratio of the opposite side to the hypotenuse in a right triangle.
sine wave  One in which amplitudes vary in proportion to the sine function of an angle.
skin effect  A term which is used to describe current flowing on the outer surface of a conductor at very high frequencies. Skin effect causes the effective resistance of a coil to increase at higher frequencies since the effect is the same as reducing the cmil area of the wire.
slew rate distortion  A distortion that occurs in op-amps when the rate of change in output voltage tries to exceed the slew rate capabilities of the op-amp.
slew-rate, SR  An op-amp specification indicating the maximum rate at which the output voltage can change. SR is specified in V / μ.
slip rings  In an ac generator, devices that provide connections to the rotor.
slow-blow fuse  A type of fuse which can handle a temporary surge current which exceeds the current rating of the fuse. This type of fuse has an element with a coiled construction and is designed to open only on a continued overload such as short-circuit.
small signal  A signal whose peak-to-peak current value is one-tenth or less the dc diode or dc emitter current.
solder  Alloy of tin and lead used for fusing wire connections.
solenoid  Coil used for electromagnetic devices.
source  One of the three leads of an FET. The source lead connects to one end of the conducting channel.
spade lug  A type of wire connector.
SPDT  Single-pole double-throw switch or relay contacts.
specific gravity  Ratio of weight of a substance with that of an equal volume of water.
specific resistance  The R for a unit length, area, or volume.
SPST  Single-pole single-throw switch or relay contacts.
square wave  An almost instantaneous rise and decay of voltage or current in a periodic pattern with time and with a constant peak value. The V or I is on and off for equal times and at constant values.
standard resistor  A variable resistor in one leg of a Wheatstone bridge which is varied to provide equal voltage ratios in both series strings of the bridge. With equal voltage ratios in each series string the bridge is said to be balanced.
static electricity  Electric charges not in motion.
stator  Stationary part of a generator or motor.
steady-state value  The V or I produced by a source without any sudden changes. Can be dc or ac value. Final value of V or I after transient.
storage cell or battery  Type that can be recharged.
stray capacitance  A very small capacitance that exists between any two conductors separated by an insulator. The capacitance can be between two wires in a wiring harness or between a single wire and a metal chassis as examples.
stray inductance  The small inductance associated with any length of conductor or component lead. The effects of both stray inductance and stray capacitance are most noticeable with very high frequencies.
string  Components connected in series.
summing amplifier  An amplifier whose output voltage equals the negative sum of the input voltages.
superconductivity  Very low R at extremely low temperatures.
superposition theorem  Method of analyzing a network with multiple sources by using one at a time and combining their effects.
supersonic  Frequency above the range of hearing, generally above 16,000 Hz.
surface-mount resistor  Resistor made by depositing a thick carbon film on a ceramic base. Electrical connection to the resistive element is made by two leadless solder, end electrodes that are C-shaped.
surface-mount technology  Components soldered directly to the copper traces of a printed circuit board. No holes need to be drilled for surface-mounted components.
susceptance (B)  Reciprocal of reactance in sine-wave ac circuits; B = 1/x.
swamping resistor  An unbypassed resistor in the emitter circuit of a common-emitter amplifier. A swamping resistor stabilizes the voltage gain and reduces distortion.
switch  Device used to open or close connections of a voltage source to a load circuit.
switching contacts  The contacts which open and close when a relay is energized.
symmetrical JFET  A JFET which has its gate regions located in the center of the channel. With a symmetrical JFET the drain and source leads can be interchanged without affecting its operation.
tail current, IT  The dc current in the emitter resistor of a differential amplifier.
tangent (tan)  Trigonometric function of an angle, equal to the ratio of the opposite side to the adjacent side in a right triangle.
tank circuit  An LC tuned circuit. Stores energy in L and C.
tantalum  Chemical element used for electrolytic capacitors.
taper  How R of a variable resistor changes with the angle of shaft rotation.
tapered control  The manner in which the resistance of a potentiometer varies with shaft rotation. For a linear taper, one-half shaft rotation corresponds to a resistance change of one-half its maximum value. For a nonlinear taper, the resistance change is more gradual at one end, with larger changes at the other end.
taut-band meter  Type of construction for meter movement often used in VOM.
temperature coefficient  For resistance, how R varies with a change in temperature.
tesla (T)  Unit of flux density, equal to 108 lines of force per square meter.
Thermistor  A resistor whose resistance value changes with changes in its operating temperatures.
Thevenin's theorem  Method of reducing a complicated network to one voltage source with series resistance.
three-phase power  AC voltage generated with three components differing in phase by 120°.
threshold voltage, VGS(th)  The minimum value of VGS in an enhancement-type MOSFET which causes drain current to flow.
Throw  The number of closed contact positions that exist per pole on a switch.
thyristor  A semiconductor device with alternating layers of P and N material that can only be operated in the switching mode where they act as either an open or closed switch.
time constant  Time required to change by 63% after a sudden rise or fall in V and I. Results from the ability of L and C to store energy. Equals RC or L/R.
Tolerance  The maximum allowable percent difference between the measured and coded values of resistance.
toroid  Electromagnet with its core in the form of a closed magnetic ring.
transconductance, gm  The ratio of the change in drain current, ΔID, to the change in gate-source voltage, ΔVGS for a fixed value of VDS. The unit of gm is the Siemen (S).
transformer  A device that has two or more coil windings used to step up or step down ac voltage.
transient response  Temporary value of V or I in capacitive or inductive circuits caused by abrupt change.
transistor  A three terminal semiconductor device which can amplify an ac signal or be used as an electronic switch.
TRIAC  A bidirectional semiconductor device that remains in a nonconducting state until the forward breakover voltage is reached. Once conducting, the voltage across the triac drops to a very low value. Like an SCR, the breakover voltage can be controlled by gate current.
trigonometry  Analysis of angles and triangles.
trivalent atom  An atom with 3 valence electrons.
troubleshooting  A term which refers to the diagnosing or analyzing of a faulty electronic circuit.
tuning  Varying the resonant frequency of an LC circuit.
turns ratio  Comparison of turns in primary and secondary of a transformer.
twin lead  Transmission line with two conductors in plastic insulator.
UHF  Ultra high frequencies in band of 30 to 300 MHz.
unijunction transistor, UJT  A 3-terminal semiconductor device that has only 1 pn junction. UJT's are used to control the conduction angle of an SCR.
unipolar  A term which describes a device having only one type of charge carrier, either electrons or holes.
universal time-constant graph  A graph which shows the percent change in voltage or current in an RC or RL circuit with respect to the number of time-constants that have elapsed.
valence electrons  Those electrons in the outermost ring or shell of an atom.
VAR  Unit for volt-amperes of reactive power, 90° out of phase with real power.
variac  Transformer with variable turns ratio to provide different amounts of secondary voltage.
vector  A line representing magnitude and direction in space.
VHF  Very high frequencies in band of 30 to 300 MHz.
volt (V)  Practical unit of potential difference. One volt produces one ampere of current in IJ a resistance of one ohm. IV = IJ / IC.
voltage divider  A series circuit to provide V less than the source voltage.
voltage drop  Voltage across each component in a series circuit. The proportional part of total applied V.
voltage follower  An op-amp circuit with unity voltage gain. A voltage follower has a very high input impedance and a very low output impedance. Voltage followers are also known unity-gain amplifiers, buffer amplifiers and isolation amplifiers.
voltage gain, AV  The ratio of output voltage to input voltage in a transistor amplifier or AV = Vout / Vin.
voltage polarity  A term which is used to describe the positive and negative ends of a potential difference across a component such as a resistor.
voltage source  Supplies potential difference across two terminals. Has internal series ri.
voltage taps  The points in a series voltage divider which provide different voltages with respect to ground.
voltaic cell  A device which converts chemical energy into electric energy. The output voltage of a voltaic cell depends on the type of elements used for the electrodes.
volt-ampere (VA)  Unit of apparent power, equal to V x I.
volt-ampere characteristic  Graph to show how I varies with V.
voltampere reactive (VAR)  The voltamperes at the angle of 90°.
voltmeter loading  The amount of current taken by the voltmeter acting as a load. As a result, the measured voltage is less than the actual value.
VOM  Volt-ohm-milliammeter.
watt (W)  Unit of real power. Equal to I2R or VI cos ø.
watt-hour  Unit of electric energy, as power x time.
wattmeter  Measures real power as instantaneous value of V x I.
wavelength (λ)  Distance in space between two points with the same magnitude and direction in a propagated wave.
wavetrap  An LC circuit tuned to reject the resonant frequency.
weber (Wb)  Unit of magnetic flux, equal to 108 lines of force.
Wheatstone bridge  Balanced circuit used for precise measurements of resistance.
wire gage  A system of wire sizes based on the diameter of the wire. Also, the tool used to measure wire size.
wire-wound resistors  Resistors made with wire known as resistance wire which is wrapped around an insulating core.
work  Corresponds to energy. Equal to power x time, as in kilowatt-hour unit. Basic unit is one joule, equal to one volt-coulomb, or one watt-second.
wye network  Three components connected with one end in a common connection and the other ends to three lines. Same as T network.
xC  Capacitive reactance equal to 1/(2πfC).
xL  Inductive reactance equal to 2πfL.
Y  Symbol for admittance in an ac circuit. Reciprocal of impedance Z; Y = 1/Z.
Y network  Another way of denoting a wye network.
Z  Symbol for ac impedance. Includes resistance with capacitive and inductive reactance.
zener current, IZ  The name given to the reverse current in a zener diode.
zener diode  A diode that has been optimized for operation in the breakdown region.
zero crossing detector  An op-amp comparator whose output voltage switches to either ±Vsat when the input voltage crosses through zero.
zero power resistance  The resistance of a thermistor with zero power dissipation, designated R0.
zero-ohm resistor  A resistor whose value is practically 0Ω. The 0Ω value is denoted by a single black band around the center of the resistor body.
zero-ohms adjustment  Used with ohmmeter of a VOM to set the correct reading at zero ohms.





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