Electric power. Electrical phenomena in nature

1. At homes, electricity is used for lighting and for operating vacuum cleaners, television sets, and other appliances to make our lives comfortable. It's also often used for cooking and heating. It's used to drive machines and computers in factories and offices. It provides power for telephone and broadcasting systems. It's used to drive electric trains, and when stored in batteries it's used to power certain motor vehicles- it's even possible to have an electrically driven car. The production of electricity supply power for all this thing is carried out by means of generators. Isolated buildings in rural areas, such as farm houses, may have small generators fuelled by petrol to make the electricity they need. Small generators like these are also used to supply electric power to settlements in developing countries. But in most industrialized nations, the making of electricity is done on a huge scale at vast electricity power stations. Here, large generators are used, but these must be driven by some kind of engine or turbine for which energy has to be provided. The turbine may be driven by steam turbine, coal, oil, or natural gas may be passed through the boiler.

2. Before electricity can reach our electric lamps, fires, and other electrically- operated equipment, it has to pass through several stages. First, it has to be made or generated at the power station, by changing one of the natural sources of energy into electrical energy. Then it has to flow through switchgear, which controls its flow and which can shut power off when necessary. From the switch-gear it goes to a transformer which increases the pressure or voltage at which it is generated ready for sending by transmission lines over long distances. High voltage enables relatively thin overhead conductors called power lines, or transmission lines, to carry large amounts of electricity over long distances. The transmission twisted like a rope around a steel core to give strength. They hang from strings of insulators which prevent the electricity escaping to earth and being wasted or giving shocks to people near the line. These transmission lines and pylons make up power networks that serve large areas of the country.

Вправа 3

Вивчіть лексику до тексту:

Rural - сільський

Switch gear - вимикач

Broadcasting system - Радіомовленнєві системи

Supply power - постачання електрики

To shut - припиняти роботу

Twisted - викривлений

Towers- вишки

Pylons - опори

Domestic voltage - внутрішня напруга

To carry large amounts- нести велику кількість

Transmission line - лнія передач

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Вправа 5

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Вправа 6

Перекладіть українською мовою:

Switch gear, pylons, domestic voltage, nuclear, generator, a flow, network, huge scale, to increase the pressure or voltage, a rope, several stages, transition.

Вправа 7

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Electric current

An electric current is a flow of electric charge, and its intensity is measured in amperes. Examples of electric currents include metallic conduction, where electrons flow through a conductor such as a metal wire, and electrolysis, where ions (charged atoms) flow through liquids. The particles themselves often move quite slowly, while the electric field that drives them propagates at close to the speed of light. See electrical conduction for more information.

Devices that use charge flow principles in materials are called electronic devices.

A direct current (DC) is a unidirectional flow, while an alternating current (AC) reverses direction repeatedly. The time average of an alternating current is zero, but its energy capability (RMS value) is not zero.

Ohm's Law is an important relationship describing the behaviour of electric currents, relating them to voltage.

For historical reasons, electric current is said to flow from the most positive part of a circuit to the most negative part. The electric current thus defined is called conventional current. It is now known that, depending on the conditions, an electric current can consist of a flow of charged particles in either direction, or even in both directions at once. The positive-to-negative convention is widely used to simplify this situation. If another definition is used - for example, "electron current" - it should be explicitly stated.

Electrical energy

Electrical energy is energy stored in an electric field or transported by an electric current. Energy is defined as the ability to do work, and electrical energy is simply one of the many types of energy. Examples of electrical energy include:

· the energy that is constantly stored in the Earth's atmosphere, and is partly released during a thunderstorm in the form of lightning

· the energy that is stored in the coils of an electrical generator in a power station, and is then transmitted by wires to the consumer; the consumer then pays for each unit of energy he receives

· the energy that is stored in a capacitor, and can be released to drive a current through an electrical circuit

Electric power

Electric power is the rate at which electrical energy is produced or consumed, and is measured in watts (symbol is: W).

A fossil-fuel or nuclear power station converts heat to electrical energy, and the faster the station burns fuel, assuming constant efficiency of conversion, the higher

its power output. The output of a power station is usually specified in megawatts (millions of watts). The electrical energy is then sent over transmission lines to reach the consumers.

Every consumer uses appliances that convert the electrical energy to other forms of energy, such as heat (in electric arc furnaces and electric heaters), light (in light bulbs and fluorescent lamps), or motion, i.e. kinetic energy (in electric motors). Like the power station, each appliance is also rated in watts, depending on the rate at which it converts electrical energy into another form. The power station must produce electrical energy at the same rate as all the connected appliances consume it.

In electrical engineering, the concepts of apparent power and reactive power are also used. Apparent power is the product of RMS voltage and RMS current, and is measured in volt-amperes (VA). Reactive power is measured in volt-amperes-reactive (VAR).

Non-nuclear electric power is categorized as either green or brown electricity.

Green power is a cleaner alternative energy source in comparison to traditional sources, and is derived from renewable energy resources that do not produce any nuclear waste; examples include energy produced from wind, water, solar, thermal, hydro, combustible renewables and waste.

Electricity from coal, oil, and natural gas is known as traditional power or "brown" electricity.

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