1、电子英语证书考试(PEC)-电子学基本词汇AALGORITHMS - A mathematical equation that produces in a fixed number of steps the answer the answer to a question or the solution to a problem. ALTERNATING CURRENT - AC VOLTAGE - Either voltage or current that varies smoothly from zero to a maximum value in one direction, or po
2、larity, and returns to zero. It then reverses its direction (polarity) and rises to a maximum value in the opposite direction, and then returns to zero to complete the cycle. This cycle is repeated continuously. The number of cycles per second is its frequency, measured in hertz (Hz). See SINE WAVE.
3、 ANALOG SIGNAL - An electrical signal that has continuously varying voltages, frequencies, or phases. AMPERE - The unit of measurement of electrical current flow, named after Andr Ampre, a 19th century French physicist. One ampere is the value of current that will be maintained in a circuit with an
4、electromotive force of one volt and a resistance of one ohm. One ampere = 6.25 x 1018 electrons/second. See CURRENT. AMPLIFICATION - The process of increasing the voltage, current, or power of an electrical or electronic signal. AMPLIFIER - An electronic circuit that draws power from a supply voltag
5、e, or voltage source, to produce, at its output, an increased reproduction of the signal existing at its input. The amplifying component could be a transistor, vacuum tube, or an appropriate magnetic device. ANALOG VOLTAGE - A gradually changing voltage. The term is interchangeable with LINEAR VOLTA
6、GE. For example, the voltage sensed by an automobiles speedometer is the analog of the speed of the automobile.NGSTROM UNIT - A unit of length that measures wavelength and is equal to 0.1 of a billionth of a meter (1x10-10 meters). It is named after Anders ngstrm, a 19th century Swedish physicist.AR
7、MATURE - The moving part of a magnetic device consisting of one or more coils that are electrically connected to create the rotatable section of a generator. See ARMATURE in Glossary of Switches, Keyboards, and Electromechanical Relays.BBATTERY - An electrical device consisting of one or more cells
8、which converts chemical or solar energy into electrical energy. A battery provides a source of steady-state DC voltage. BLOW TIME - The maximum time required for a fuse to open after being subjected to an excess of the devices rated current. Fuses are classified by blow time as slow, normal, or fast
9、. CCELL - A single unit of a battery that generates a DC voltage by converting chemical or solar energy into electrical energy. CIRCUIT - A single component or group of interconnected components powered by a source of voltage and configured according to specified rules. A circuit performs a specific
10、 or a predetermined general task. CIRCUIT BREAKER - An automatic, magnetic, or bimetallic device that will open a current-carrying circuit causing the circuit to become inoperative. This device is used to prevent circuit damage under a condition of excess current. Unlike a fuse that melts when its r
11、ating is exceeded, a circuit breaker can be reset automatically or manually when the circuit problem is corrected. COIL - A length of insulated wire wound around a laminated iron or steel core, a ferrite or powdered iron core, or a non-ferrous material such as ceramic aluminum, or plastic. A non-fer
12、rous core is called an “air core“since it is non-magnetic in nature. COMPONENT - An individual part or element of an electrical or electronic circuit which performs a designated function within that circuit. It may consist of a single part, a combination of parts, or assemblies. CONDUCTOR - A metal
13、material that allows electrical current to flow and has essentially zero resistance. CURRENT - The movement of electrons per second through a conductor or a component. It is measured in amperes and is designated by the letter, I. There are 6.25 x 1018 electrons per second in one ampere. (1018 = a bi
14、llion billion) DDECAY TIME - The time it takes for a voltage to be reduced to a given percent of the peak voltage. See ELECTROSTATIC DISCHARGE. DELAY TIME - The time it takes for a circuit breaker to open after its rated current is exceeded. See BLOW TIME. DIGITAL VOLTAGE - A discontinuous or step-f
15、unction electrical pulse characterized by an instantaneous change from zero to some finite level, either in a positive or negative direction with respect to a reference. DIRECT CURRENT - DC - An electrical current or voltage with a constant direction (polarity) with respect to a fixed reference. DC
16、can be either positive or negative. EELECTRICAL GENERATOR - An assembly consisting of a magnet mounted on a frame, and a wire coil (armature) that can be rotated within the magnetic field. The function of the generator is to convert mechanical energy into electrical energy. See TURBINE. ELECTRODES -
17、 Conductive metallic strips normally inserted into an electrolyte to provide the chemical action needed to convert chemical energy into electrical energy. ELECTROLYTE - A solution of specific chemicals in a battery which convert chemical energy into electrical energy. ELECTROMOTIVE FORCE (EMF) - The
18、 electrical force that exists across the terminals of an electrical generator, or battery. When connected to a load in a closed circuit, this force produces a voltage across the load and causes current to flow in that circuit. EMF is measured in volts and designated with the letter E (supply voltage
19、) or V (load voltage). ELECTRON - Considered to be the smallest unit of electrical charge. ELECTROSTATIC CHARGE - The accumulation of electrons on the surface of a nonconducting material when it is rubbed by another nonconducting material. See TRIBOELECTRIC EFFECT. ELECTROSTATIC DISCHARGE (ESD) - A
20、transfer of an electrostatic charge between a material with an excess of electrons and a material with a deficiency of electrons. EXPONENTIAL SYSTEM - A convenient means of notating large and small numbers using a base number and a superscript, e.g., 102.FFREQUENCY (f) - The number of cycles per sec
21、ond of an AC wave measured in hertz (Hz). FUNDAMENTAL FREQUENCY - The lowest frequency of a complex AC waveshape represented by a single sine wave. FUSE - A short strip of metal having extremely low resistance and functioning as a protective device in a circuit. A fuse will melt when its rated curre
22、nt is exceeded, thereby opening the circuit. GGROUND - The part of a circuit or system that is the reference for the voltages existing in that circuit or system. The ground consists of a material such as copper, steel, aluminum, or any other conductive material. See REFERENCE.HHARMONICS - Multiples
23、of a single sine wave (the fundamental frequency). The even harmonics are the 2nd, 4th, 6th, etc., and the odd harmonics are the 3rd, 5th, 7th , etc. All harmonics are multiples of their fundamental frequency. HEAT SINK - A metal base or plate onto which one or more components are mounted to absorb,
24、 carry away, or radiate the heat generated by the component(s). Overheating may result in the malfunction or destruction of the part(s) generating the heat or might cause damage to other parts of the circuit. HERTZ (HZ) - The unit of measurement of the frequency of a sine wave or square wave, named
25、after Heinrich Hertz, a 19th century German physicist. The term hertz designates the number of cycles per second exhibited by these waves. HORSEPOWER (HP) - A unit of measurement of mechanical power. It indicates the ability of a device or mechanism to do a specific amount of work over a period of t
26、ime. It is equal to 550 foot-pounds per second in mechanical power or 746 watts in electrical power. LLIGHTNING ARRESTOR - A protective device that provides a very low resistance path to any voltage above its rated value. See METAL OXIDE ELEMENT. LINE VOLTAGE - The AC voltage supply that provides th
27、e prime source of electrical power for office, laboratory, factory, and home electrical and electronic equipment. Throughout North, Central, and South America, the line voltage is nominally specified as 120 volts AC, at 60 hertz. In Europe, the line voltage is nominally specified as 240 volts AC, at
28、 50 hertz. Line voltage can be either privately or publicly generated. LOAD - A device, component, appliance, system, or machine to which an electrical force (voltage) is applied. Resistance is inherent in the structure of a load and is an integral part of an electrical or electronic circuit. MMETAL
29、 OXIDE ELEMENT - A resistive device that protects against excess voltage surges in a circuit. It is called a metal oxide varistor (MOV). Below its rated voltage, its extremely high resistance has no effect on a circuit. Above its rated voltage, it sharply changes to an extremely low value resistor.
30、See LIGHTNING ARRESTOR. NONCONDUCTOR (INSULATOR) - A material that has essentially infinite resistance (generally greater than 1010 ohms). It protects the circuit by isolating components and conductors from each other to prevent them from touching each other, thereby avoiding the possibility of a sh
31、ort circuit.OOHM - The unit of measurement of resistance symbolized by the Greek letter, omega (W). It is named after George Ohm, a 19th century German physicist. One ohm is the value of resistance through which an electromotive force of one volt will maintain a current of one ampere. See RESISTANCE
32、. OHMS LAW - The relationship that exists between the electrical parameters of voltage (electrical pressure), resistance (the opposition to the voltage), and current (the flow of electrons in the circuit). Ohms Law states that the amount of current flowing in a circuit is equal to the applied voltag
33、e divided by the circuit resistance.PPERIOD - The time required to complete one cycle of AC and is calculated as the reciprocal of the frequency (1/f). It is measured in seconds and designated with the letter T. PHOTOVOLTAIC EFFECT - The generation of an electrical current in a circuit containing a
34、photosensitive device when the device is illuminated by visible or nonvisible light. POWER - The rate at which work is done and measured in watts (W). In electrical and electronic circuits, Power (P) = Supply Voltage (E) x Supply Current (I) or Load Voltage (VL) x Load Current (IL). See WATT. PROTEC
35、TED AREA - An area equipped with appropriate ESD protective materials and equipment. It provides a site where ESD voltage is limited below the ESD sensitivity level of the component or equipment being handled or manufactured. PULSATING DC VOLTAGE - Rectified AC voltage, either positive or negative,
36、with respect to a reference. Half-wave pulsating DC voltage uses only one-half of the available AC voltage. Full-wave DC voltage uses both halves of the AC voltage waveshape.RREFERENCE - An arbitrarily selected point or section of a circuit or system to which the polarities and values of the circuit
37、 voltages are referred. See GROUND. RELIABILITY - The assurance that a component will perform in a specified manner for a specified time under a set of specified conditions that include electrical, mechanical, thermal, and environmental stresses. The concept of reliability encompasses the elements o
38、f both quality and longevity. See STABILITY. RESISTANCE - The electrical characteristic of a component, material, circuit, or system which acts to limit current in a circuit. It is measured in ohms (W) and designated with the letter R. Resistance depends on the molecular structure and dimensions of
39、a component or device and on the configuration of a circuit or system. See OHM.SSINE WAVE - A smooth, continuously moving waveshape that has no break in its appearance. It has positive and negative half-cycles that are generally symmetrical with respect to a reference. The cyclical repetition of the
40、se waves produces a waveshape that has a specified frequency in hertz (number of cycles per second) and a specified amplitude. SQUARE WAVE - A rectangular-shaped (step-function) periodic wave with a positive and negative half-cycle of equal lengths of time or duration. A square wave consists of a si
41、ne waves fundamental frequency combined with the odd harmonics (multiples) of its fundamental frequency. STABILITY - The ability of a component, circuit, or system to maintain a fixed level of operation within specified tolerances under varying external conditions. Changing conditions include voltag
42、e, frequency, temperature, and longevity. See RELIABILITY. STEADY-STATE DC VOLTAGE - A fixed polarity of positive or negative voltage with respect to a reference. This form of voltage is used as the power source for electronic circuits.TTEMPERATURE COEFFICIENT (TC) - The change in the characteristic
43、 of a component which occurs because of a change in temperature. TC can be specified either as the number of parts per million (ppm) change per C change in temperature, or as a percent change in value per C change in temperature. TRIBOELECTRIC EFFECT - The phenomenon of transferring electrons from o
44、ne nonconductive material to another when friction is produced between them. See ELECTROSTATIC CHARGE. TURBINE - A mechanical structure with rotatable blades mounted onto its assembly and mechanically coupled to an electrical generator. When a turbine is placed in the path of flowing water, steam, o
45、r moving air, the movement of the water, steam, or air across the blades causes them to turn. The generators armature rotates within a magnetic field which produces electrical energy at the terminals of the generator. See ELECTRICAL GENERATOR.VVARISTOR - A metal (zinc) oxide over-voltage protective
46、device. See METAL OXIDE ELEMENT. VOLT - The unit of measurement of electromotive force necessary to produce one ampere of current in a circuit having a total resistance of one ohm. The volt is named for Alessandro Volta, an 18th century Italian physicist. VOLTAGE - The electromotive force that exist
47、s across a voltage source (supply voltage) or a load in a circuit. Its unit of measurement is a volt. See ELECTROMOTIVE FORCE. VOLTAGE ARRESTOR - A fast-acting, over-voltage protective device that can absorb or short a voltage to ground when the voltage is in excess of the devices rated value.WWATT
48、- The unit of measurement for electrical power, named after James Watt, an 18th century Scottish engineer. One watt of power is dissipated when a voltage of one volt is applied across a load of one ohm resulting in one ampere of current in the circuit. See POWER.WAVELENGTH - The physical distance between the beginning and the end of a cycle in a periodic wave (sine wave or square wave) as it travels through space or through a conductor. Wavelength is measured in meters (or in ngstrom units) and is designated with the Greek letter lambda (l).
