Electrical and electronics engineering

Electrical and electronics engineering is the largest and most diverse field of engineering. Among the most important subjects in the field are electric power and machinery, electronic cir­cuits, control systems, computer design, superconduc­tors, solid-state electronics, medical imaging systems, robotics, lasers, radar, consumer electronics, and fibre optics. Despite its diversity, electrical engineering can be di­vided into four main branches: electric power and ma­chinery, electronics, communications and control, and computers.

Electric Power and Machinery

The field of electric power is concerned with the de­sign and operation of systems for generating, transmit­ting, and distributing electric power Engineers in this field have brought about several important developments since the late 1970s. One of these is the ability to trans­mit power at extremely high voltages in both the direct current (DC) and alternating current (AC) modes, reduc­ing power losses proportionately. Another is the real-time control of power generation, transmission, and dis­tribution, using computers to analyse the data fed back from the power system to a central station and thereby optimizing the efficiency of the system while it is in op­eration.

A significant advance in the engineering of electric machinery has been the introduction of electronic con­trols that enable AC motors to run at variable speeds by adjusting the frequency of the current fed into them. DC motors have also been made to run more efficiently this way.

Electronics

Electronic engineering deals with the research, de­sign, integration, and application of circuits and devices used in the transmission and processing of information. Information is now generated, transmitted, received, and stored electronically on a scale unprecedented in history, and there is every indication that the explosive rate of growth in this field will continue unabated.

Electronic engineers design circuits to perform spe­cific tasks, such as amplifying electronic signals, add­ing binary numbers, and demodulating radio signals to recover the information they carry. Circuits are also used to generate waveforms useful for synchronization and timing, as in television, and for correcting errors in dig­ital information, as in telecommunications.

Prior to the 1960s, circuits consisted of separate elec­tronic devices — resistors, capacitors, inductors, and vacuum tubes — assembled on a chassis and connected by wires to form a bulky package. The electronics revo­lution of the 1970s and 1980s set the trend towards inte­grating electronic devices on a single tiny chip of silicon or some other semi-conductive material. The complex task of manufacturing these chips uses the most advanced technology, including computers, electron-beam lithog­raphy, micro-manipulators, ion-beam implantation, and ultraclean environments.

Communications and Control

Engineers work on control systems ranging from the everyday, passenger-actuated, such as those that run a lift, to the exotic, such as systems for keeping spacecraft on course. Control systems are used extensively in air­craft and ships, in military fire-control systems, in power transmission and distribution, in automated manufac­turing, and in robotics.

Computers

Computer engineering is now the most rapidly grow­ing field. The electronics of computers involve engineers in design and manufacture of memory systems, of cen­tral processing units, and of peripheral devices. The field of computer science is closely related to computer engi­neering; however, the task of making computers more «intelligent» (artificial intelligence), through creation of sophisticated programs or development of higher level machine languages or other means, is generally regarded as the aim of computer science.

One current trend in computer engineering is micro­miniaturization. Engineers try to place greater and greater numbers of circuit elements onto smaller and

smaller chips. Another trend is towards increasing the speed of computer operations through the use of parallel processors and superconducting materials.

HARDWARE

What is hardware? Webster's dictionary gives us the following definition of the hardware —themechanical, magnetic, electronic, and electrical devices composing a computer system.

Computer hardware can be divided into four catego­ries:

1. input hardware; 2. processing hardware; 3. storage hardware; 4.output hardware. Some of them are presented here.

Input hardware

The purpose of the input hardware is to collect data and convert it into a form suitable for computer process­ing. The most common input device is akeyboard. It looks very much like a typewriter. Themouse is a hand held device connected to the computer by small cable. As the mouse is rolled across the mouse pad, the cursor moves across the screen. When the cursor reaches the desired location, the user usually pushes a button on the mouse once or twice to signal a menu selection or a command to the computer.

Thelight pen uses a light sensitive photoelectric cell to signal screen position to the computer. Another type of input hardware is optic-electronicscanner that is used to input graphics as well as typeset characters.Micro­phone andvideo camera can be also used to input data into the computer. Electronic cameras are becoming very popular among the consumers for their relatively low price and convenience.

Processing hardware

The purpose of processing hardware is retrieve, inter­pret and direct the execution of software instructions provided to the computer. The most common components of processing hardware are the Central Processing Unit and main memory.

The Central Processing Unit (CPU) is the brain of the computer. It reads and interprets software instructions and coordinates the processing activities that must take place. The design of the CPU affects the processing power and the speed of the computer, as well as the amount of main memory it can use effectively. With a well-designed CPU in your computer, you can perform highly sophisti­cated tasks in a very short time.

Memory is the system of component of the computer in which information is stored. There are two types of computer memory: RAM and ROM.

RAM (random access memory) is the volatile compu­ter memory, used for creating loading, and running pro­grams and for manipulating and temporarily storing data;

ROM (read only memory) is nonvolatile, nonmodifiable computer memory, used to hold programmed in­structions to the system.

The more memory you have in your computer, the more operations you can perform.

WHO DISCOVERED ELECTRICITY?

The story of the discovery of electricity is connected with the name of Thales, the Greek philosopher. The story goes that one day Thales rubbed a piece of amber against his sleeve and found to his great surprise that it attracted small bits of dried leaves. After further experimenting he concluded that this attractive force was a property that amber alone possessed.He called this characteristic "electricity" because the Greek word for amber was electron.

Thales' great discovery remained a curiosity for more than twothousand years. Then many other substances were found to have this curious property of electricity too. Naturally the peopleof the past had no idea of what electricity was. They thought of it as "rays" or "stream" that passed from the rubbed material. There were scientists who thought electric­ity to be a sort of "fluid" that flowed through wires as water flows through pipes. Later many of them found out that elec­tricity was made of tiny particles of some kind. In this way they tried to separate electricity into individual particles. There were some attempts to weigh a single particle of elec­tricity and calculate its electric charge. This was one of the most delicate weighing jobs ever done by a man, for a single electric particle weighs only about half a millionth of a mil­lionth of a millionth of a millionth of a millionth of a pound. To make up a pound, it would take more of those particles than there are drops of water in the Atlantic Ocean. Now we know these electric particles to be electrons.

When a large number of electrons break away from their atoms and move through the wire, we describe this action by saying that electricity is flowing through the wire and the electrical "fluid" that scientists of the past talked about is nothing else than electrons flowing along a wire. A lot of scientists worked in the field of electricity doing their best to make the life of people good and happy.

MICROWAVE PROCESSING

The project on microwave processing of food is being carried out by research groups of theUniversity of Bristol.

Over the past five years, the work has particularly focused on pro­cessing and preservation systems for the safe and efficient production of foods, including microwave pasteurisation and sterilisation.

The overall aim of this project will be to establish an understanding of the relationship between microwave and food parameters during processing and maintenance of food quality and safety. This will be achieved bу the development of computer models of process in combination with experimental investigations at pilot-plant scale.

The most promising commercial applications for microwave processing in the areas of pasteurisation are:

1. Identify the most promising operational strategies required in terms of microwave power, frequency, process time and configuration of microwave cavity, to ensure foods safety and quality;

2. Determine the safe storage lives for microwave pasteurisation products;

3. Investigate pressure build-up and other factors controlling package failure during processing;

4. Provide product data on composition, temperature and configuration of the raw materials required for control systems in programmable microwave units;

5. Provide processing data on the time, power and field distribution required to temper particular raw materials to an optimum state for the next processing operation.

Notes:

microwave - микроволновый in terms of - исходя из, на основе

at pilot - в масштабе опытного завода failure - повреждение

promising - многообещающий to temper - делать

7. MACHINE-TOOLS

Machine-tools are used toshape metals and other materials. The material to be shaped is called theworkpiece, Most machine-tools are nowelectricallydriven. Machine-tools with electrical drive are faster and moreaccurate than hand tools: they were an important element in thedevelopment of mass-production processes, as they allowed individual parts to be made in large numbers so as to beinterchangeable.

All machine-tools havefacilities for holding both the workpiece and the tool, and for accurately controlling the movement of the cutting toolrelative to the workpiece. Most machining operations generate largeamounts of heat, and use coolingfluids (usually a mixture of water and oils) for cooling andlubrication.

Machine-tools usually work materials mechanically but other machining methods have been developed lately. They include chemical machining,spark erosion to machine very hard materials to any shape by means of a continuous high-voltagespark (discharge) between an electrode and a workpiece. Other machining methods includedrilling using ultrasound, and cuttingby means of a laserbeam. Numerical control of machine-tools andflexible manufacturing systems have made it possible for complete systems of machine-tools to be used flexibly for the manufacture of arange of products.

Пояснения к тексту:

Machine-tools – станки

Workpiece – деталь

Spark erosion – электроискровая обработка

Range – ассортимент, диапазон

RESISTANCE AND RESISTIVITY.

Every material offers some resistance to the flow of an electric current through it. The resistance of a conductor depends on its material. It also depends on its temperature. Materials change the value of resistance with change in their temperature. Different materials also have different melting points. Good conductors, like the metals copper, silver, and aluminium, offer very little resistance, while non-conductors, like glass, wood and paper, offer a very high resistance. The resistance of nichrome is rather high.

Resistance of conductors and their resistivity have different units. The unit by which resistance is measured is called the ohm, in honour of the German physicist Ohm.

The unit, of resistance is the ohm while the unit of resis­tivity is the ohm • m. The standard international ohm is de­fined as the resistance offered to a steady electric current by a column of mercury 1 sq.mm in cross-section and 106.3 cm long at a temperature of 0°.

There are several factors that determine the electrical re­sistance of any wire: a) the material which it is composed of; b) the size of the wire; c) its temperature.

In more general terms, the resistance of a wire is propor­tional to its length and inversely proportional to its cross-sectional area (provided the temperature of a conductor re­mains constant). This is Ohm's law.

ELECTRIC POWER PLANTS.

Electric power is generated at electric power plants. The main unit of an electric power plant comprises a prime mover and the generator which it rotates.

In order to actuate the prime mover energy is required. Many different sources of energy are in use nowadays. To these sources belong heat obtained by burning fuels, pressure due to the flow of air (wind), solar heat, etc.

According to the kind of energy used by the prime move: power plants are divided into groups. Thermal, hydraulic (water-power) and wind plants form these groups. According to the kind of prime mover, electric power plants are classed as:

a) Steam turbine plants, where steam turbines serve as prime movers. The main generating units at steam turbine plants belong to the modern, high-capacity class of
power plants.

b) Steam engine plants, in which the prime mover is a piston-type steam engine.

Nowadays no large generating plants of industrial importance are constructed with such prime movers. They are used only for local power supply.

c) Diesel-engine plants; in them diesel internal combustion engines are installed. These plants are also of small capacity, they are employed for local power supply.

d) Hydroelectric power plants employ water turbines as prime movers. Therefore they are called hydroturbine plants. Their main generating unit is the hydrogenerator.

Modern wind-electric power plants utilize various turbines: these plants as well as the small capacity hydroelectric power plants are widely used in agriculture.

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