2_kurs_4_semestr

Current Electricity

Current is the rate of flow of electrons. It is produced by moving electrons and it is measured in amperes. Unlike static electricity, current electricity must flow through a

conductor, usually copper wire. Current with electricity is just like current when you think of a river. The river flows from one spot to another, and the speed it moves is the speed of the current. With electricity, current is a measure of the amount of energy transferred over a period of time. That energy is called a flow of electrons. One of the results of current is the heating of the conductor. When an

electric stove heats up, it's because of the flow of current.

There are different sources of current electricity including the chemical reactions taking place in a battery. The most common source is the generator. A simple generator produces electricity when a coil of copper turns inside a magnetic field. In a power plant, electromagnets spinning inside many coils of copper wire generate vast quantities of current electricity.

There are two main kinds of electric current: Direct (DC) and Alternating (AC). It‘s easy to remember. Direct current is like the energy you get from a battery. Alternating current is like the plugs in the wall. The big difference between the two is that DC is a flow of energy while AC can turn on and off. AC reverses the direction of the electrons.

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What is happening when two objects are rubbed together and static electricity results?

What is the difference between DC and AC electricity? Identify some common sources of each type of electricity.

Make a plan of the text.

Retell the text using your plan.

Answer the following questions.

1)What property of matter causes the electric force?

2)How can rubbing two objects together make one object positive and the other object negative?

3)Explain how you can use an electroscope to detect charge.

Write one complete sentence for each term listed below.

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GRAMMAR

May – Might – Could

 possibility (present/future)

may/might/could + present infinitive = it is possible/it is likely/perhaps

-Where‘s Aunt Julia?

-She may/might/could still be at work.

(= It‘s possible that she‘s still at work.)

 possibility (past) may/might/could + perfect infinitive = it was possible, perhaps

a) We use these structures to refer to a past action which was possibly true.

e.g. ‗The lights are still on.‘

‗Helen may/might/could have forgotten to turn them off.‘ (Perhaps

Helen forgot/has forgotten to turn them off.)

b) We also use them to refer to things which were possible but did not

happen. May is not normally used in this case.

e.g. Why did you run across the road?

You might/could have been killed. (Luckily, you weren‘t killed.)

 We use May I …?/Could I …?/Can I …? to ask for permission

Note the difference in the following questions.

May I use your telephone? (Formal – we do not know the other person very

well.)

Can I use your phone? (Informal – we know the other person very well.)

Could I use your phone? (more polite than ‗can‘.)

 giving/refusing permission

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a) may/can = you are allowed to do smth

We use may and can, but not might or could, to give permission. May is very formal and is not used in everyday speech.

e.g. You can sit here if you like. (everyday speech)

Passengers may take only one item of hand luggage on board. (written

notice)

Note: We use Could I …? to ask permission, can or may, but not could, to reply.

e.g. ‗Could I leave a little earlier?‘ ‗Yes, you can.‘/ ‗Yes, you may.‘

b) can’t/may not = you are not allowed to do smth

We use can‟t and may not, but not couldn‟t, to refuse permission. e.g. Students may not wear outdoor shoes on the basketball court.

(= Students aren‘t allowed to …) I‘m sorry, but you can’t park here.

(NOT: I‘m sorry, but you couldn‘t park here.)

 requests

May/Might/Can/Could I …?

We use these structures to ask for something politely. Might I …? is more formal than May I …? and is not often used.

May/Can/Could I have a pen and some paper, please?

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4.I …a new dress. I haven‘t really got enough money.

5.We … the Smiths. There is a film on TV we want to watch.

6.Let‘s take Molly to the funfair. She …it.

7.Mother …something special tonight. It‘s my birthday.

8.I …work early today. I have almost finished everything I have to do.

9.Sally …home late tonight. She‘s got a lot of work at the office.

2. Answer the questions according to the model.

Model: When Ann is going to leave?

She may leave next week.

1.When are you going to visit your grandmother?

2.When is your mother going to go shopping?

3.When are the students going to on an excursion?

4.When is your friend going to go to Canada?

5.When is she going to type an article?

6.When are you going to finish the work?

3. Translate into English.

1.Можна сісти?

2.Можу я зачинити вікно?

3.Я можу прийти заздалегідь.

4.Ти зможеш пообідати зі мною.

5.Вона, можливо, хвора.

6.Можна цьому хлопчикові погратися твоїми іграшками?

7.Можна мені ввімкнути світло?

8.Завтра, можливо, буде злива.

9.Можливо, вона забула твою адресу.

10.Можна нам користуватися словниками?

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UNIT 10

Electric Current

Read the text and translate it into Ukrainian.

The electric current was born in the year 1800 when Volta constructed the first source of continuous current. Since that time numerous scientists and inventors, Russian and foreign, have greatly contributed to its development and practical application.

As a result, we cannot imagine modern civilization without the electric current. We can‘t imagine how people could do without electric lamps, without vacuum cleaners, refrigerators, washing machines and other electrically operated devices that are widely used today. In fact, telephones, lifts, electric trams and trains, radio and television have been made possible only owing to the electric current.

Electric energy finds its most important use in industry. Take, for example, the electric motor transforming electric energy into mechanical energy. It finds wide application at every mill and factory. As for the electric crane, it can easily lift objects weighing hundreds of tons.

Ever since Volta first produced a source of continuous current, men of science have been forming theories on this subject. For some time they could see no real difference between the newly-discovered phenomenon and the former understanding of static charges. Then the famous French scientist Ampere (after whom the unit of current was named)

determined the difference between the current and the static charges. In addition to it, Ampere gave the current direction: he supposed the current to flow from the positive pole of the source round the circuit and back again to the negative pole.

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We consider Ampere to be right in his first statement but he was certainly wrong in the second, as to the direction of the current.

Let us turn our attention now to the electric current itself. The current which flows along wires consists of moving electrons. What can we say about the electron? We know the electron to be a minute particle having an electric charge. We also know that that charge is negative. As these minute charges travel along a wire, that wire is said to carry an electric current.

In addition to traveling through solids, however, the electric current can flow though liquids as well and even through gases. In both cases it produces some of most important effects to meet industrial.

Some liquids, such as melted metals for example, conduct current without any change to themselves. Other, called electrolytes are found to change greatly when the current passes through them.

You know the main kinds of the electric current (AC and DC) from the previous text.

What do you remember about direct current (DC) and alternating current (AC)? What are they used for?

Answer the following questions:

1.What does electric current do to muscle tissue?

2.What can electric current do to motor muscles (fingers, arms, legs)?

3.What can electric current do to heart and lungs?

4.Why should you use one hand while working on live power circuits? Which hand?

5.Why is water dangerous when working around electric power?

6.Why is metal jewelry dangerous to wear when working on electric circuits?

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7.What kinds of tools are best for working on live power circuits?

8.What kind of immediate medical attention does an electric shock victim require? CPR if they are not breathing or their heart is not beating.

9.What footwear is appropriate when working around electric power?

10.What footwear is not appropriate when working around electric power?

Present your reports on the outstanding scientists worked in the field of electricity.

Individual Work

Explore by Reading

Important Names in Electricity

1.Go to the library and read about the work of the following scientists: Georg S. Ohm, André Marie Ampère, and Alessandro Volta.

2.On a separate piece of paper, answer the following questions:

1)What unit of electricity is named after each of these scientists?

2)Which scientist‘s work was ignored for a long time?

3)Who invented the electric battery?

4)Who discovered that an electric current could decompose water?

5)Which scientist found out that an electric current flowing through a coiled wire acts like a magnet?

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GRAMMAR

Must – Have to – Mustn‟t / Needn‟t

Must – Have to

 Must and have to express obligation and necessity. e.g. You must come home early.

I have to be at the office at nine o‘clock.

 Must can only be used in the present tense. We use have to to form all other tenses.

e.g. I‘ll have to work late tomorrow.

He had to leave early yesterday. (NOT: He must leave early yesterday.)

 We also use must to give advice.

e.g. You must talk to your brother about it. You mustn’t be late for school.

Mustn’t – Needn’t

 Must not/Mustn‟t (you aren’t allowed to/it is against the rules) expresses prohibition.

e.g. You mustn’t park here. (It is against the rules.)

Needn‟t (it isn’t necessary) expresses lack of necessity. We can use don‟t/doesn‟t have to instead of needn’t with no difference in

meaning.

e.g. You needn‘t/don‘t have to buy me a gift.

(It isn‘t necessary for you to buy me a gift.)

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