ТОП 10:

ELECTRONICS AND TECHNICAL PROGRESS



Large – scale application of electronic techniques is a trend of technical progress capable of revolutionizing many branches of industry.

Electronics as a science studies the properties of electrons, the laws of their motion, the laws of the transformation of various kinds of energy through the media of electrons.

At present it is difficult to enumerate all branches of science and technology which are based on electronic technique.

Electronics make it possible to raise industrial automation to a higher level, to prepare conditions for the future technical retooling of the national economy. It is expected to revolutionize the system of control over mechanisms and production processes. Electronics greatly helps to conduct fundamental research in nuclear physics, in the study of the nature of matter, and in realization of controlled thermonuclear reactions.

An ever greater role is being played by electronics in the development of the chemical industry.

Electronics embrace many independent branches. The main among them are vacuum, semiconductor, molecular and quantum electronics.

 

TEXT 6

PROTECTION AND CONTROL EQUIPMENT

In electrical systems for the generation, distribution and use of electrical energy, considerable control equipment is necessary. It can be divided into two classes:

a) equipment used at the generating and distributing end;

b) equipment used at the receiving end of the system.

c) secondary emission, in which electrons are driven from a material by the impact of electrons or other particles on its surface.

d) field emission, in which electrons are drawn from the surface of a metal by the application of very powerful electric fields.

 

TEXT 7

THE NUCLEUS

The nucleus is composed of protons, neutrons, and other subatomic particles. The proton is a relatively heavy positive particle. It has exactly the same quantity of electrical charge as the electron although its sign (or value) is opposite. The proton weighs the same as approximately 1845 electrons, and the atom contains a like number of protons and electrons. The neutron is so named because it is electrically neutral, that is, it is neither positive nor negative. The neutron adds weight to the atom and tends to prevent movement of the protons.

When the parts of the atom are examined, there can be found minute particles with positive and negative electrical charges. The basic difference between lead and gold lies in the number of electrons and protons in the atoms which compose these materials (metals).

The simplest atom consists of a nucleus which contains one proton, which is orbited by a single electron. This is the hydrogen atom. One of the more complex atoms is californium. This atom contains 98 photons and 98 electrons with the electrons orbiting the nucleus in seven different and distinct energy shells.

 

TEXT 8

WHAT IS AN ELECTRON?

What is an electron? It is a very small, indivisible, fundamental particle – a major constituent of all matter. All electrons appear to be identical and to have properties that do not change with time.

Two essential characteristics of the electron are its mass and its charge.

Qualitatively, an electron is a piece of matter that has weight and is affected by gravity. Just as the mass of any object is defined, the mass of the electron can be defined by applying a force and measuring the resulting rate of change in the velocity of the electron, that is, the rapidity with which its velocity changes. This rate of change is called acceleration, and the electron mass is then defined as the ratio of the applied force to the resulting acceleration. The mass of the electron is found to be about 9.11 Ч 10-28 grams. Not only the electron but all matter appears to have positive mass, which is equivalent to saying that a force applied to any

abject results in acceleration in the same direction as the force.

How does the other aspect, the charge of the electron, arise? All electrons have an electric charge, and the amount of charge, like the mass, is identical for all electrons. No one has ever succeeded in isolating an amount of charge smaller than that of the electron. The sign of the charge of the electron is conventionally defined as negative; the electron thus represents the fundamental unit of a negative charge.

 

TEXT 9

ELECTRONS AND ELECTRONIC CHARGES

An atom of ordinary hydrogen is composed of one positively charged proton as a nucleus and one negatively charged electron. The proton is about 1,840 times more massive than the electron. Heavier atoms are built up of protons, neutrons, and electrons. When a body is negatively charged, it has excess electrons; if positively charged, there is a deficiency of electrons.

In metallic conductors many of the electrons are free to travel about among the atoms like molecules of a gas.

When electric charges are static, they do not progress in any definite direction. Excess electrostatic charges reside on the outer surface of a conductor, and their density is greatest in regions of greatest curvature.

 

TEXT 10

POLARITY

All matter is basically composed of two types of electricity: positive particles and negative particles. The negative particles are relatively light in weight and in constant motion. These orbiting particles exhibit equal and opposite electrical characteristics to the heavier particles within the nucleus.

When an atom has the same number of electrons as it has protons, it exalts no outward electrical properties. This is because the positive and negative charges are exactly balanced. Such an atom is electrically stable and is said to be neutral.

When an atom takes on an excess of electrons, it exhibits outward characteristics similar to the electron. It takes an overall negative property. This condition is called a negative change, and such changed atom is not electrically stable. A charged atom is called an ion, and if the charge is negative, it is called a negative ion.

An atom which has less than its normal quota of electrons, displays a positive polarity similar to that of the proton due to the fact that it has more positive protons than it has negative electrons. This type of atom is said to assume a positive electrical charge. Such an atom is known as a positive ion while it is in this electrically unstable condition.

These charges of atoms are the simplest examples of static electricity. We stated that atoms are influenced to accept or give up electrons.

As the name dynamic electricity indicates, this is electricity in motion.

The heart of the matter is electron movement.

In electrical system, electrical pressure is needed. To maintain this pressure, a device that will move electrons in a way similar to that in which the pump moves water is necessary. The most familiar is the storage battery.

 

TEXT 11

ENERGY CONVERSION

Since energy can neither be created nor destroyed, any process of producing voltage must be a conversion from one form of energy to another. There are several names for the machines that convert mechanical energy into electrical energy. The dynamo is the source of huge amounts of power; the magneto supplies minute power outputs; and in between there are alternators and generators. All of these work at the same principle, the principle demonstrated by Faraday when he discovered that relative motion between a magnetic field and a conductor in that field would induce a current in the conductor. It makes no real difference whether the conductor is stationary and the field moving or the field is stationary and the conductor moving. The important factor is the relative motion in a manner that will cause flux to cut across the conductor.

 

 

ЛИТЕРАТУРА

1. Комолова З. П., Новоселецкая В. П., Новикова Н. В. Популярная электроника. – М.: ВШ, 1988. – 157 с.

2. Бахчисарайцева М. Э., Каширина В. А., Антипова А. Ф. English for Power Engineering Students. – М.: ВШ, 1983. – 155 с.

3. Кабо П. Д., Фомичева С. Н. Popular Science Reader. – М.: Просвещение, 1983. – с. 28–37.

4. Четвертакова М. М. Сборник текстов по электротехнике – Санкт-Петербург, 1999. – 48 с.

5. Беляева М. А., Голова З. С., Иванова А. П., Арутюнова К. М. Сборник технических текстов на английском языке. Учебное пособие для ВТУЗов. Под ред. Н. В. Володина. – М.: Изд-во литературы на иностранных языках. 1959.

 

 







Последнее изменение этой страницы: 2016-06-23; Нарушение авторского права страницы

infopedia.su Все материалы представленные на сайте исключительно с целью ознакомления читателями и не преследуют коммерческих целей или нарушение авторских прав. Обратная связь - 34.236.245.255 (0.007 с.)