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Учебное пособие I приборы.rtf
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5. Use the words in brackets (...) to complete the sentences.

1. I can't use my office at the moment. It …is being painted… (paint)

2. We didn't go to the party. We...weren't invited...(not/invite).

3. The washing machine was broken but it's OK now. It...........................(repair).

4. The washing machine..............................................(repair) yesterday afternoon.

6. How old are these houses? When.....................................................(they/build)?

7. A: ................................................................(the computer / use) at the moment?

B: Yes, Jim is using it.

8. I've never seen these flowers before. What........................................(they/call)?

9. Some trees....................................................(blow) down in the storm last night.

10. The bridge is closed at the moment. It..................................................(damage) last week and it................................(not/repair) yet.

Learn the vocabulary

consist (of) состоять (из)

contain содержать, container контейнер

divide (into) - делить (на)

inner - внутренний

nucleus - ядро, nuclei - ядра , nuclear - ядерный

outer - внешний

possible - возможный, impossible - невозможный, possibly - возможно, possibility - возможность

several - несколько,

shell – оболочка, ,

substance - вещество,

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Matter

Matter consists of one or more elements. Elements are substances that cannot be divided into other substances. An atom is the smallest particle of an element, which has all the properties of the element and can take part in chemical reactions.

In each atom there is a nucleus, containing a number of protons (each proton has a positive electrical charge) and a number of neutrons, having no electrical charge. The nucleus is surrounded by a number of electrons. Each electron has a negative electrical charge. The electrons orbit around the nucleus. An atom has as many protons as it has electrons. This results in a zero electrical charge of the atom. Electrons orbit around the nucleus in one of the several possible orbits. These orbits are called shells.

In a silicon atom there are fourteen protons in the nucleus. Fourteen electrons orbit around the nucleus in three orbits. The first or inner shell contains two electrons and cannot hold any more electrons. In the second shell there are eight electrons. It cannot hold additional electrons either. In the third shell there are only four electrons. This shell can hold more electrons. The outer shell of any atom is called its valence shell. The number of electrons in the valence shell is known as the valency of the atom.

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CONDUCTORS, SEMICONDUCTORS AND INSULATORS

Materials can be classed in three groups according to their electrical properties — conductors, semiconductors and insulators. Metals such as silver , copper, and aluminium have many free electrons. This makes it easy for current to flow through them. Therefore, these metals are called conductors.

Materials such as glass , rubber , and many plastics have practically no free electrons. This makes it very difficult for current to flow through them. These materials are known as insulators and are used in many fields ranging from the covering on conductors to the dielectric in capacitors .

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