文档介绍：自动化专业英语
English for Automation
Contents
Unit 1
Unit 2
Unit 3
Unit 4
Unit 5
Unit 6
Unit 7
Unit 8
Unit 9
Unit 10
主编黄星王晓平
副主编蒋凌张巍赵九九
主审黄晶
Reading A
Unit 1
The ponents used in electronics are of two general types: passive (. resistors and capacitors) and active (. transistors and integrated circuits). The main difference between active and ponents is that active ones require to be powered in some way to make them work.
ponents
The Resistor
A resistor (Figure 1-1) is a piece of material that obeys Ohm's Law. The es from its main property; it resists the flow of charge through itself, hence allowing us to control the current. Resistors can be made of various kinds of material, but whatever the choice it must conduct some electricity otherwise it wouldn't be of any use.
Two wires are connected to opposite ends of the resistor (Figure 1-2). When we apply a potential difference between the wires we set up a current from one wire to the other, through the resistor. The size of the current is proportional to the difference in voltage between the wires. The resistance (in units of Ohms) is defined as the ratio of the applied voltage, V (in Volts), divided by the current, I (in Amps), produced by the applied voltage.
Unit 1
The value is usually displayed using standard colour code (Figure 1-3).
Unit 1
The Capacitor
If you look at a catalogue of ponents you'll find an enormous variety of sizes and types of capacitor. However, for most purposes we can divide capacitors into two basic types: dielectric and electrolytic.
A capacitor acts as a charge store (Figure 1-4). It contains a pair of metal plates separated by a thin sheet of insulating material. The plates are electrically neutral - the number of positive protons in each exactly equals the number of negative electrons.
However, if we connect wires to the plates and apply external voltage we can drag electrons off one plate and push them on to the other.
Unit 1
This takes energy, . we have to