Иностранный язык (Методические указания)

In most objects, all of the forces are in balance. Half of the electrons are spinning in one direction; half are spinning in the other. These spinning electrons are scattered evenly throughout the object.

Magnets are different. In magnets, most of the electrons at one end are spinning in one direction. Most of the electrons at the other end are spinning in the opposite direction. This creates an imbalance in the forces between the ends of a magnet. This creates a magnetic field around a magnet. A magnet is labeled with North (N) and South (S) poles. The magnetic force in a magnet flows from the North pole to the South pole.

If you try to push the South poles together, they repel each other. Two North poles also repel each other. Turn one magnet around and the North

(N) and the South (S) poles are attracted to each other. Just like protons and electrons, opposites attract. These special properties of magnets can be used to make electricity. Moving magnetic fields can pull and push electrons. Some metals, like copper have electrons that are loosely held. They can be pushed from their shells by moving magnets. Magnets and wire are used together in electric generators.

(980)

10.1Answer the following questions

1.What is magnetism?

2.What is called the North (South) pole?

3.When do poles repel each other?

4.When do poles attract each other?

11 Batteries produce electricity

A battery produces electricity using two different metals in a chemical solution. A chemical reaction between the metals and the chemicals frees more electrons in one metal than in the other. One end of the battery is attached to one of the metals; the other end is attached to the other metal. The end that frees more electrons develops a positive charge and the other end develops a negative charge. If a wire is attached from one end of the battery to the other, electrons flow through the wire to balance the electrical charge. A load is a device that does work or performs a job. If a load––such as a lightbulb –– is placed along the wire, the electricity can do work as it flows through the wire.

(700)

11

11.1 Find and read all the international words in the text.

12 Direct current and alternating current

We know that current is the flow of electricity through a circuit. There are two main types of current: direct and alternating. When electrons flow in one direction only, the current is called a direct current. When electrons flow first in one direction and then in another in a periodic manner, the current is called an alternating current. An alternating current is a current that changes its direction of flow through a circuit in a periodic manner. Alternating current flows in cycles. The number of cycles per second is termed the frequency of current. In a 60-cycle alternating current circuit, the current flows in one direction 60 times per second and in the other direction 60 times per second.

A standard frequency has a great advantage since different electrical systems can be interconnected.

(800)

12.1Answer the questions

1. What is current?

2. What types of current do you know?

3. What type is termed a direct current ( an alternating current)? 4. In what manner does an alternating current flow?

5. What is frequency?

12.2Test. Choose the correct variant

1. Direct current …

a)changes its direction of flow

b)flows in one direction

2. The frequency of the circuit is … a) the number of cycles per minute

12

b) the number of cycles per second

3. A standard frequency has …

a)great advantages

b)disadvantages

13 Conductors

According to their conductivity all materials are divided into conductors, insulators and semiconductors. Conductors allow electricity to pass through them; insulators do not. Conductors are materials having a very high conductivity. A conductor owes its conducting powers to the presence of free electrons which have broken away from their atoms. The most common of them are metals (copper, aluminium, steel and others), carbon and electrolytes. Their coefficient of resistance is different. Copper, for example has a positive coefficient while carbon has a negative coefficient of resistance.

According to their resistivity, conductors are divided into two groups; the first includes materials with low resistivity; copper, aluminium and others. These metals are used to produce wire conductors due to their high mechanical strength. The second group includes materials with high resistivity: one of these is nichrome. Due to its good heat resistance, nichrome is used to produce heaters. Carbon is commonly used to produce electrodes and brushes for electric machines.

(920)

13.1 Answer the questions

1.Into what groups are materials divided?

2.What do conductors do?

3.What materials are common conductors?

4.What metals have high mechanical strength?

13.2 Test. Choose the correct variant

1.All materials are divided into

a)conductors and semiconductors

b)conductors, insulators and semiconductors

2.Copper has

a)high mechanical strength

13

b)low mechanical strength

3.Carbon has

a)a positive coefficient of resistance

b)a negative coefficient of resistance

4.Copper is commonly used to produce

a)heaters

b)brushes

14 Insulators

Insulating materials have a very low conductivity. They offer extremely high resistance to the flow of current. Insulators are used in electric devices to isolate conductors. Thus they should have a high dielectric strength and a high resistivity. Their mechanical properties are also important for practical use.

Insulators are divided into gaseous, liquid, solid. They are also divided into groups according to their heat resistance.

The main gaseous insulator is air. The dielectric strength of air is extremely low; it is lower than the strength of most liquid and solid dielectrics. Liquid insulators are mineral oils, synthetic liquids, resins, and others. Mineral oils are used in oil transformers, cables and capacitors. In transformers, oil is used to insulate current conducting parts. As to resins, at low temperatures they are amorphous. When heated, they become first plastic, then liquid. Resins are the most important components of many plastics. Plastics are used as wire and cable insulation. Solid insulators are paper, cloth, plastics, porcelain, and clastomers. Plastics are widely used in electrical engineering as insulating and structural materials.

(1000)

14.1. Answer the questions

1.What materials offer high resistance?

2.Where are insulators used?

3.What properties of insulators are important for practice?

4.Into what groups are insulators divided?

5.What is the main gaseous insulator?

6.What are liquid insulators?

14.2Test. Choose the correct variant

14

1.Insulators offer

a)extremely high resistance

b)extremely low resistance

2.They should have

a)a high dielectric strength

b)a low electric strength

3.Their mechanical properties

a)are important for practice

b)are not important for practice

4.Commonly used insulating materials are

a)liquid

b)gaseous

c)solid

15 Transmission of electric power

Electric power is generated at power plants and it must be transmitted to other parts of the country. Thick wires carry electric power over long distances. The wires are not always made of copper, often they are made of other metals.

A number of wires put together form one thick cable. A cable consists of a number of wires put together and a pair consists of two insulated conductors forming a metallic circuit. Thus the basic transmission element of communications is a long transmission line. A cable is the main part of this long transmission line. Nowadays the electricity is transmitted over long distances and the length of transmitting power lines varies from area to area.

(570)

15.1 Answer the following questions

1.Where is electric power generated?

2.What carries electric power over long distances?

3.What is the main part of the transmission line?

4.What elements form one thick cable?

15.2 Choose the correct variant:

1.The transmission line may consist of …

a)thick wires

15

b)long and thick copper wires

c)thick copper cables

d)metallic conductors

2.Thick cables …

a)carry electric power

b)form the main part of the line

c)carry electric current

15.3Translate the following word combinations: copper wire; power plants; electric cable; metallic cable; metallic circuit; metallic conductor; insulated conductor; insulated circuit of transmission line; a number of cables; thick wire; main parts; a number of pairs; this part; thick cables.

16 Electric lines and their efficiency

Wires are used to deliver electric power and to interconnect different components of electrical installations. Conductors used for electric wiring are commonly produced of copper and aluminium. Aluminium is widely used nowadays due to its low cost. Copper is also widely used in electrical engineering but its cost is much higher.

Wires connecting the components of various installations may be insulated. They may also be used without insulation. In long wires (longer than 10m), power loss cannot be ignored since it is rather high. Power loss in a line should not exceed a definite value. If this value is exceeded the line becomes inefficient.

One should know that the efficiency of a line is not constant – it may change. The value of the line efficiency depends on the load: the greater the load the lower is the line efficiency. At voltage losses of 2 to 5 per cent the efficiency of a line is 98 – 95 per cent. Protecting devices, fuses and relays are used to protect the circuit against overcurrents and short – circuits.

(860)

16.1 Complete the sentences using the correct variant

16

16.2 Answer these questions

1.Why is aluminium widely used nowadays?

2.What does the efficiency of a line depend on?

3.What are fuses used for?

4.When does a line become inefficient?

17 How electricity is generated

An electric generator is a device for converting mechanical energy into electrical energy. The process is based on the relationship between magnetism and electricity. When a wire or any other electrically conductive material moves across a magnetic field, an electric current occurs in the wire. The large generators used by the electric utility industry have a stationary conductor. A magnet is positioned inside a stationary conducting ring that is wrapped with wire. When the magnet rotates, it induces a small electric current in each section of wire as it passes. Each section of wire constitutes a small, separate electric conductor. All the small currents of individual sections add up to one current of considerable size. This current is what is used for electric power.

An electric utility power station uses either a turbine, engine, water wheel, or other similar machine to drive an electric generator or a device that converts mechanical or chemical energy to generate electricity. Steam turbines, internal-combustion engines, gas combustion turbines, water turbines, and wind turbines are the most common methods to generate electricity. Most power plants are about 35 percent efficient. That means that for every 100 units of energy that go into a plant, only 35 units are converted to usable electrical energy.

(1120)

17

17.1Translate the following word combinations used in the text: longdistance power transmission, radio transmitters, alternating current generators, wire cable, heat losses, power line, transmission line, at the city end.

17.2Find synonyms: to step up, part, to step down, to increase, to decrease, not far, section, different, near, various.

17.3Form new words using suffixes: generate, relate, transmit, transform, receive, distant, consume.

18 Electric motors

We know that a motor is an electric rotating machine converting electrical energy into mechanical energy.

Mechanical energy is converted by a generator into electrical energy. To utilize that generated energy, we need another machine that will reconvert electrical energy back into mechanical energy. Such a machine is the electric motor.

Electric motors are used in industry, transport, mines, business, farms and even houses. They are the moving elements in various household appliances, such as vacuum cleaner, washing machine, refrigerator, and the like.

Trams, local trains and trolley buses are powered by electric motors, thus, providing cities with clean, fast, comfortable transportation.

And in each of the places, where they work, the electric motors produce just the desirable kind of motion, speed, and power. As is well known, motors are standardized in sizes, types, and speeds. They are available in various sizes, from a small fraction of a horse-power (h. p.) to many thousands of horse-power. Motors are also available in a wide range of speeds. Their speed may be fixed (or synchronous), constant for given load conditions, adjustable, or variable. Many are self-starting and reversible.

(1020)

18.1 Answer the following questions

1.What is a motor?

2.What machine reconverts electrical energy into mechanical energy?

18

3.Where are motors used?

4.In what household appliances are motors used?

18.2 Translate the following words and define their part of speech:

1.consume, consumption, consumer;

2.generate, generation, generator, degenerate;

3.efficient, efficiency, efficiently;

4.construction, construct, constructor, reconstruct, reconstruction;

5.convert, conversion, convertible, converter, reconvert.

19

English – Russian vocabulary

A

Accident – авария, катастрофа, несчастный случай according to – в соответствии

accumulation – накопление

actual – действительный, подлинный actuate – побуждать

add – дополнять, прибавлять

adjust – регулировать; приспосабливать advantage – выгода, польза; преимущество affect – воздействовать

afford – быть в состоянии сделать что-л. аir – воздух

allow – позволять; предоставлять; допускать although – хотя

among – среди, между

amorphous – бесформенный, аморфный amount – количество

ancient – древний another – другой

apart – в стороне, особняком, отдельно appliance – устройство, прибор

application – заявление, просьба; применение apply – применять, использовать

arc – (эл.) дуга

arouse – пробуждать; вызывать; возбуждать asbestos – асбест

assemble – сборка, монтаж assume – предполагать, допускать at least – по крайней мере

attain – достигать

attend – посещать, присутствовать attract – привлекать

automatic – автоматический automobile – автомобиль auxiliary – вспомогательный

available – наличный, имеющийся в распоряжении

20