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Reading.
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| properties – свойства | cell – батарейка |
| flow of charges – поток зарядов | voltage source – источник напряжения |
| power supply – источник питания | to join – соединять |
| current – ток | to complete circuit – замыкать цепь |
| through wires – по проводам | to break – размыкать |
| circuit [׳ sә: kit] – цепь | broken circuit – разомкнутая цепь |
| switch – выключатель, переключатель | to burn out – перегорать |
| to connect – соединять | fault [fo: lt] – повреждение, обрыв |
| resistance – сопротивление | to open – размыкать |
| such as – такой как | short circuit – короткое замыкание |
| battery lead – вывод батареи | open circuit – разомкнутая цепь |
| capacitor [ kә ׳ pæ sitә ] – конденсатор | series connection – последовательное соединение |
| to extend – расширять | parallel connection – параллельное соединение |
| to glow – светиться | mixed connection – смешанное соединение |
| supply voltage – напряжение питания | to blow – перегорать |
| to go out – погаснуть | identical – одинаковый |
| ampere [׳ æ mpε ә ] – ампер | combined resistance – суммарное сопротивление |
| to add up – суммироваться | LED (light emitting diode) [lаit i׳ mitiη dаi׳ oud] – светодиод |
| reciprocal [ri׳ siprә kә l] – обратная величина | to replace – заменять |
Text 1
Electricity
It is impossible to imagine our civilization without electricity: economic and social progress will be turned to the past and our daily lives completely transformed.
Electrical power has become universal. Thousands of applications of electricity such as lighting, electrochemistry and electrometallurgy are longstanding and unquestionable.
With the appearance of the electrical motor, power cables replaced transmission shafts, gear wheels, belts and pulleys1 in the 19th century workshops. And in the home a whole range of various time and labour saving appliances2 have become a part of our everyday lives.
Other devices are based on specific properties of electricity: electrostatics in the case of photocopying machine and electromagnetism in the case of radar and television. These applications have made electricity most widely used.
The first industrial application was in the silver workshops in Paris. The generator – a new compact source of electricity – was also developed there. The generator replaced the batteries and other devices that had been used before.
Electric lighting came into wide use at the end of the last century with the development of the electric lamp by Thomas Edison. Then the transformer was invented, the first electric lines and networks were set up, dynamos and induction motors3 were designed.
Since the beginning of the 20th century the successful development of electricity has begun throughout the industrial world. The consumption of electricity has doubled every ten years.
Today consumption of electricity per capita4 is an indicator of the state of development and economic health of a nation. Electricity has replaced other sources of energy because it offers improved service and reduced cost.
One of the greatest advantages of electricity is that it is clean,
easily-regulated and generates no by-products5. Applications of electricity now cover all fields of human activity from house washing machines to the latest laser devices. Electricity is the efficient source of some of the most recent technological advances such as the laser and electron beams. Truly6 electricity provides mankind with the energy of the future.
Notes:
1. transmission shafts, gear wheels, belts and pulleys – трансмиссионные валы, зубчатые колеса, ремни и блоки
2. time and labour saving appliances – электроприборы, экономящие время и труд
3. induction motors – индукционные моторы
4. per capita – на человека; на душу населения
5. by-products – побочные продукты
6. truly – поистине
Answer the questions:
1. What is this text about?
2. What industrial applications of electricity do you know?
3. What home applications of electricity do you know?
4. Where was the generator developed?
5. Who invented the electric lamp?
6. Do you know who invented the dynamo?
7. Can you imagine our life without electricity? Why?
V. Составьте предложения из двух частей:
| 1. Electricity | 1. have already become universal. |
| 2. The application of electricity in the home and industry | 2. has completely transformed our everyday life. |
| 3. Electricity was used for the first time | 3. per capita is an indicator of a nation state development. |
| 4. The generator, a new source of electricity | 4. the wide industrial use of electricity has begun throughout the world. |
| 5. Since the beginning of the 20th century | 5. was also developed in Paris. |
| 6. Today consumption of electricity | 6. for industrial purposes in the silver workshops in Paris. |
VI. Заполните пропуски следующими словами:
electricity increase consumers power use generation reduce consumption far users application provide sources energy light
We hear so much these days of local problems of electricity (1).... Many (2)... are taking steps to (3)... their electricity (4)....This is as a result of the recent (5)... in electricity tariffs for (6).... We should all try to (7)... less (8)..., by insulating our houses, turning off the (9)... when leaving a room and using less hot water.
We must try to develop alternative (10)... of energy to (11)... electricity for domestic and industrial (12).... It is known that nuclear power comes to the consumer as electricity, which is clean and convenient form (13).... Although nuclear (14)... stations are large, they can be built (15)... from places where people live.
VII. Расскажите об электричестве и его применении, пользуясь вопросами, данными ниже, в качестве плана:
1. What is electricity? (a source of electric power used in every day life and industry)
2. What are the sources of electricity? (batteries, generators, electric motors and many other devices)
3. What properties of electricity have made it widely used? (electrostatics and electromagnetism)
4. What are the advantages of electricity? (clearness, easy regulation, no byproducts, low cost, improved service)
5. What are home uses of electricity? (lighting, heating, various time and labour saving appliances, radio, television, video and many others)
6. What are the latest industrial applications of electricity? (lasers and electronic devices)
Text 2
Electricity
Electricity is the flow of charge around the circuit carrying energy from the battery (or power supply) to components such as lamps and motors.
Electric current can flow only if a circuit is complete. Electric current flows through wires from the battery to circuit components and back to the battery again.
Fig.1
This diagram shows a simple circuit. The components of the circuit are a battery, wires, a switch and a lamp. Battery gives energy to the lamp. The wires connect the components of the circuit. The switch breaks the circuit.
When the switch is open the circuit is broken, electric current cannot flow, and the lamp is off. When the switch is closed electricity flows around the circuit and the lamp is on.
What is “open circuit”? We say “open circuit” when there is no connection. “Open circuit” is a break in some part of a circuit (for example a switch in the open or off position) or a fault (for example a broken wire or burnt out component).
What is “short circuit”? A “short circuit” is a connection with very low resistance such as a wire which provides a very easy way for current. A short circuit is a fault or wrong connection. For example: if the battery leads contact one another they create a connection with very low resistance and make a short circuit. Current will flow through this short circuit instead through the circuit. This stops the circuit working. Short circuit can be the cause of a fire, because large current flows through the leads and the battery, and they will become very hot.
Text 3
Parallel and Series Circuits
Type 1. Connection in series
Fig.1
When components are connected in series (Fig. 1) each component has the same current. The battery voltage is divided between the two lamps. Each lamp will have half the voltage if the lamps are identical.
Type 2. Connection in parallel
Fig.2
When components are connected in parallel (Fig. 2) each component has the same voltage. Both lamps have the full battery voltage. The battery current is divided between the two lamps.
The terms ‘series circuit’ and ‘parallel circuit’ are simetimes used, but only the simplest of circuits are one type or the other. It is better to say that some components are connected in series or connected in parallel. Most circuits have a mixture of series and parallel connections.
Fig.3
For example: the circuit (Fig. 3) has a resistor and LED connected in series and two lamps connected in parallel. The switch is connected in series with the two lamps.
Lamps in Series
If several lamps are connected in series they will all be switched on and off together by a switch connected anywhere in the circuit. The supply voltage is divided equally between the lamps (if they are all identical). If one lamp blows all the lamps will go out because the circuit is broken.
Lamps in Parallel
If several lamps are connected in parallel each lamp has the full voltage. The lamps may be switched on and off indepentently by connecting a switch in series with each lamp. This arrangement is used to control the lamps in buildings. This type of circuit is often called a parallel circuit, but the switches and lamps are connected in series, and every pair of switch and lamp is connected in parallel.
Resistors connected in Series
When resistors are connected in series their combined resistance is equal to the individual resistances added together. For example if resistors R1 and R2 are connected in series their combined resistance, R, is given by: R = R1 + R2. Note that the combined resistance in series will always be greater than any of the individual resistances.
Resistors connected in Parallel
When resistors are connected in parallel their combined resistance is less than any of the individual resistances. There is a special equation for the combined resistance of two resistors R1 and R2:
For more than two resistors connected in parallel a more difficult equation must be used. This adds up the reciprocal of each resistance to give the reciprocal of the combined resistance:
Combined resistance in parallel will always be less than any of the individual resistances.
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