[align=left]I
IC
Abbreviation for "integrated circuit"
IC voltage regulator
Three terminal device used to hold the output voltage of a power supply constant over a wide range of load variations.
IGFET
Insulated gate field effect transistor. Another name for a "MOSFET."
impedance
(Z) Measured in ohms it is the total opposition to the flow of current offered by a circuit. Impedance consists of the vector sum of resistance and reactance.
impedance coupling
Coupling of two signal amplifier circuits through the use of an impedance such as a inductor.
impedance matching
Matching the output impedance of a source to the input impedance of a load to attain maximum power transfer.
incandescence
State of a material when heated to the point where it emits light. (red hot or white hot).
induced voltage
Voltage generated in a conductor when subjected to a moving magnetic field.
inductance
Property of a circuit to oppose a change in current. The moving magnetic field produced by a change in current causes an induced voltage to oppose the original change.
inductive circuit
Circuit having greater inductive reactance than capacitive reactance.
inductive reactance
Opposition to the flow of AC current produced by an inductor. Measured in Ohms and varies in direct proportion to frequency.
inductor
Length of conductor used to introduce inductance into a circuit. The conductor is usually wound into a coil to concentrate the magnetic lines of force and maximize the inductance. While any conductor has inductance, in common usage the term inductor usually refers to a coil.
infrared
Electromagnetic heat radiation whose frequencies are above the microwave frequency band and below red in the visible band.
inhibit
To stop an action or block data from passing.
in phase
When two or more waves of the same frequency have their positive and negative peaks occurring at the same time.
input impedance
Opposition to the flow of signal current at the input of a circuit or load.
insulated
When a non conducting material is used to isolate conducting materials from one another.
insulating material
Material that will prevent the flow of current due to its chemical composition.
insulation resistance
Resistance of insulating material. The greater the insulation resistance, the better the insulation.
integrated
When two or more components are combined into a circuit and then incorporated into a single package.
integrator
A device that approximates and whose output is proportional to an integral of the input signal. A low pass filter.
intermediate frequency amplifier
In a superheterodyne radio it amplifies a fixed frequency lower than the received radio frequency and higher than the audio frequency.
intermittent
A fault occurring at random intervals of time. Intermittent problems are often difficult to locate because of the random nature. They often don’t occur when the technician is present.
internal resistance
Every source has some resistance in series with the output current. When current is drawn from the source some power is lost due to the voltage drop across the internal resistance. Usually called output impedance or output resistance.
intrinsic material
A semiconductor material with electrical properties essentially characteristic of ideal pure crystal. Essentially silicon or germanium crystal with no measurable impurities.
intrinsic stand-off ratio
A unijunction transistor (UJT) rating used to determine the firing potential of the device.
inverting amplifier
An amplifier that has a 180° phase shift from input to output.
inverting input
In an operational amplifier (op amp) the input that is marked with a minus sign. A signal applied at the inverting input will be given 180° phase shift between input and output.
ion
An atom with fewer electrons in orbit than the number of protons in the nucleus is a positive ion. An atom with a greater number of electrons in orbit than the number of protons in the nucleus is a negative ion.
ionized
Atoms become ionized when they gain or lose a valence electron.
=================================== =============== =====================
J
j
A prefix used to indicate an imaginary number. (Operator j)
jack
Socket or connector into which a plug may be inserted.
JFET
Abbreviation for "Junction field effect transistor".
joule
The unit of work and energy.
junction
Contact or connection between two or more wires or cables. The area where the p-type material and n-type material meet in a semiconductor.
junction diode
diode. A semiconductor diode in which the rectifying characteristics occur at a junction between the n-type and p-type semiconductor materials.
=================================== =============== ===============
K
kilo
Metric prefix for 1000. (103)
kilovolt-ampere
1000 volts at 1 ampere.
kilowatt-hour
1000 watts for 1 hour.
kilowatt-hour meter
A meter used by electric utility companies to measure the amount of electric power used by a customer.
kinetic energy
Energy associated with motion.
Kirchhoff"s current law
The sum of the currents flowing into a point in a circuit is equal to the sum of the currents flowing out of that same point.
Kirchhoff"s voltage law
The algebraic sum of the voltage drops in a closed path circuit is equal to the algebraic sum of the source voltages applied.
knee voltage
The voltage at which a curve joins two relatively straight portions of a characteristic curve. For a PN junction diode, the point in the forward operating region of the characteristic curve where conduction starts to increase rapidly. For a zener diode, the term is often used in reference to the zener voltage rating.
=================================== =============== ========================
L
lag
Difference in time between two waveforms of the same frequency expressed in degrees. Example: One waveform lags another waveform by a certain number of degrees.
laminated core
Core made up of sheets of magnetic material insulated from one another by an oxide or varnish.
lamp
Device that produces light.
laser
Device that produces a very narrow intense beam of light. The name is an axcronym for "light amplification by stimulated emission of radiation.
lead
The angle by which one alternating signal leads another in time. Opposite of lag. Also a wire that connects two points in a circuit.
lead-acid cell
Cell made up of lead plates immersed in a sulphuric acid electrolyte. An automobile battery usually consists of six lead-acid cells.
leakage
Small undesirable flow of current through an insulator or dielectric.
LED
Abbreviation for "light emitting diode."
left-hand-rule
If fingers of the left hand are placed around a wire so that the thumb points in the direction of electron flow, the fingers will be pointing in the direction of the magnetic field being produced by the conductor.
Lenz’s law
The current induced in a circuit due to a change in the magnetic field is so directed as to oppose the flux, or to exert a mechanical force to oppose the motion.
level detector
An op-amp circuit that compares two inputs and provides a DC output indicating the polarity relationship between the inputs. A comparitor.
light
Electromagnetic radiation in a band of frequencies that can be received by the human eye.
lifetime
The time from the creation of an electron hole pair until recombination occurs.
light-emitting diode
A semiconductor diode that converts electric energy into electromagnetic radiation at a visible and near infrared frequencies when its pn junction is forward biased.
limiter
Circuit or device that prevents some portion of its input from reaching the output. A clipper.
linear
Relationship between input and output in which the output varies in direct proportion to the input.
linear scale
A scale in which the divisions are uniformly spaced.
line regulation
The ability of a voltage regulator to maintain a constant voltage when the regulator input voltage varies.
live
Term used to describe a circuit or piece of equipment that is on and has current flow within it.
load
A source drives a load. Whatever component or piece of equipment is connected to a source and draws current from a source is a load on that source.
load current
Current drawn from a source by a load.
load impedance
Vector sum of reactance and resistance in a load.
loading effect
Large load impedance will draw a small load current and so loading of the source is small. (light load). A small load impedance will draw a large load current from the source. (heavy load).
load regulation
The ability of a voltage regulator to maintain a constant output voltage under varying load currents.
load resistance
Resistance of a load.
logic
Science of dealing with the principle and applications of gates, relays and switches.
loss
Term used to describe a decrease in power.
low pass filter
A tuned circuit designed to pass all frequencies below a designated cut-off frequency.
=================================== =============== ======================[/align]
رد مع اقتباس
مواقع النشر (المفضلة)