Lesson 4 Electronic Components 电子元件

Text

1.Resistor

A resistor is a two-terminal electronic component that resists the flow of electrical current[1] (Fig. 2-1) . The current flowing through a resistor is directly proportional to[2] the voltage across the resistor’s terminals. This relation is represented with a well-known Ohm’s law: V = IR[3].

The ohm (symbol: Ω) is the unit of electrical resistance. Color bands are usually used to represent the resistance value (Fig. 2-2) . The first and second band represent the numerical value of the resistor, the third band specify the power-of-ten multiplier, and the fourth band if present, indicates tolerance of value in percent. The color bands are always read from left to right, and there is a gap between the third and the fourth bands to distinguish left from right.

For example, a resistor with bands of yellow, violet, red, and gold will have first digit 4 (yellow) , second digit 7 (violet) , followed by 2 (red) zeros: 4,700 ohms. Gold signifies that the tolerance is ±5%, so the real resistance could lie anywhere between 4,465 and 4,935 ohms.

2.Capacitor

A capacitor is an electronic component consisting of a pair of conductors separated by a dielectric (Fig. 2-3) . A capacitor can store electrical charge in an electrical field. Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass[5], in filter networks for smoothing the output of power supplies, in the resonant circuits for tuning radios to particular frequencies and for many other purposes.

The farad (symbol: F) is the unit of capacitance. Values of capacitance are usually specified in ranges of microfarads (μF 10-6 ) , nanofarads (nF 10-9) , or picofarads (pF 10-12) (Fig. 2-4) .

3.Inductor

An inductor is an electronic component that can store energy in a magnetic field created by the electric current passing through it[7](Fig. 2-5) . Typically an inductor is a conducting wire shaped as a coil[8], the loops helping to create a strong magnetic field. Inductors can be used to block AC signals from passing through a circuit.

The Henry (symbol: H) is the unit of inductance.

4.Transformer

A transformer is an electrical component that converts AC electricity from one voltage to another with little loss of power. The input coil is called the primary winding and the output coil is called the secondary winding. There is no electrical connection between the two coils, instead they are linked by an alternating magnetic field created in the core of the transformer [9](Fig. 2-6) .

5.Diode

A diode is a two-terminal semiconductor device that consists of a PN junction made of semiconductor material[10](Fig. 2-7) . The most common function of a diode is to allow an electric current to pass in one direction (called the diode’s forward direction) , while blocking current in the opposite direction (the reverse direction) (Fig. 2-8) .

6.Transistor

A transistor (Fig. 2-9) is a semiconductor device used to amplify electronic signals. The transistor amplifies current, and the amount of current amplification is called the current gain. In many circuits a resistor is used to convert the changing current to a changing voltage, so the transistor is being used to amplify voltage. There are two types of transistors. A bipolar junction transistor (BJT) has terminals labeled base, collector, and emitter. A small current at the base terminal (that is, flowing from the base to the emitter) can control or switch a much larger current between the collector and emitter terminals[11]. For a field-effect transistor (FET) , the terminals are labeled gate, source, and drain, and a voltage at the gate can control a current between source and drain (Fig. 2-10) .

7.Integrated Circuit

An integrated circuit (IC) , sometimes called a silicon chip or chip, is a semiconductor wafer on which thousands or millions of tiny resistors, capacitors, and transistors are fabricated[12] (Fig. 2-11) . An IC can function as an amplifier, oscillator, timer, counter, computer memory, or microprocessor.

New Words and Technical Terms

Notes to the Text

[1]electronic component that resists the flow of electrical current：that引导定语从句，修饰electronic component。句子可以翻译为：一种抵抗电流流动的电子元件。

[2]be directly proportional to：与……正比于。be inversely proportional to与……成反比。

[3]V = IR：读为V is equal to I times R。

[4]Resistor Color Code：电阻器色标。色环电阻是最多应用于各种电子设备的电阻类型，安装、维修都能方便地读出其阻值，便于检测和更换。

[5]in electronic circuits for blocking direct current while allowing alternating current to pass：for引导目的状语，其后使用V+ing形式。句子可以翻译为：在电子电路中，为了阻止直流电流同时允许交流电流通过。

[6]Parallel plate capacitor model：平行板电容器模型。

[7]an electronic component that can store energy in a magnetic field created by the electric current passing through it：that引导定语从句，修饰electronic component；created by…修饰a magnetic field。句子可以翻译为：一个电子元件能够在由通过它的电流形成的磁场中储存能量。

[8]a conducting wire shaped as a coil：一种绕成线圈形状的导线。

[9]instead they are linked by an alternating magnetic field created in the core of the transformer：created过去分词修饰an alternating magnetic field。句子可以翻译为：相反，它们是由变压器铁芯产生的交变磁场联结在一起。

[10]semiconductor device that consists of a PN junction made of semiconductor material：that引导定语从句修饰semiconductor device。句子可以翻译为：一个由半导体材料生成的PN结组成的半导体器件。

[11]A small current at the base terminal can control or switch a much larger current between the collector and emitter terminals：在基极端的小电流可以控制或开关更大的集电极和发射极之间的电流。

[12]a semiconductor wafer on which thousands or millions of tiny resistors, capacitors, and transistors are fabricated：on which引导从句，修饰a semiconductor wafer。句子可以翻译为：一个半导体晶片，在它上面制造有成千上万个微小的电阻、电容和晶体管。

Exercises

Ⅰ.Choose the best technical term to complete the following statements.

1.( ), ( ) and ( ) are electronic components.

A. vacuum tube B. integrated circuit C. silicon D. transistor

2.The kilo-ohm is the unit of ( ).

A. inductance B. resistance C. weight D. capacitance

3.( ) are used to tune radios to particular frequencies in the resonant circuits .

A. resistor B. transformer C. capacitor D. inductor

4. ( ) is an electronic component made of semiconductor material.

A. transformer B. transistor C. PN junction D. integrated circuit

5.A small current flowing from the ( ) to the ( ) can control a much larger current between the collector and emitter terminals.

A. P type semiconductor B. N type semiconductor C. emitter D. base

6.When reverse-biased, an ideal ( ) would block all current. A real one lets perhaps 10 microamperes through–not a lot, but still not perfect.

A. forward B. switch C. resistor D. diode

Ⅱ.Translate the following sentences into Chinese.

1.Resistors restrict the flow of electric current, for example a resistor is placed in series with a light-emitting diode (LED) to limit the current passing through the LED.

2.Resistance is measured in Ω. 1Ω is quite small so resistor values are often given in kΩ and MΩ. 1kΩ = 1000Ω. 1MΩ = 1000,000Ω.

3.Capacitors store electric charge. There are many types of capacitor but they can be split into two groups, polarized and unpolarized.

4.Capacitance is measured in farads, symbol F. However 1F is very large, so prefixes are used to show the smaller values. Three prefixes (multipliers) are used, μ (micro) , n (nano) and p (pico) : μ means 10-6, n means 10-9 , p means 10-12.

5.A system-on-a-chip (SoC or SOC) is a integrated circuit in which all the components needed for a computer or other system are included on a single chip.

6.A sensor is a device used to measure a physical quantity such as temperature, humidity, pressure or loudness and convert it into an electronic signal.