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 …

1. thick wires

2. long and thick copper wires

3. thick copper cables

4. metallic conductors

1. Thick cables …

1. carry electric power

2. form the main part of the line

c) carry electric current

15.3 Translate 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.

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16.1 Complete the sentences using the correct variant

1. Aluminium is used due to its a) high cost

b) low cost and high efficiency

2. Cross-section of different conductors a) varies

b) is the same

3. Power loss can be ignored a) in short wires

b) in long wires

4. A definite value of loss a) can be exceeded

b) should not be exceeded

6. Installations are protected a) by switches

b) by fuses

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.

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

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

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