Предыдущая страница реферата | 1  2  3  4  5

Conductors And Non-Conductors.

The ease with which this is done depends on the atomic constitution of the body. In some substances electrons move fairly easily, while in others they find movement difficult. This difference is expressed by what is called the electrical conductivity of the body. Substances through which electrons move easily are called good conductors. Generally speaking, among solids metals are good conductors and non-metals are poor conductors. If materials are arranged in the order of their conductivity it is found although there is no sudden transition from a group of very good to a group of very bad conductors, the atoms are restored to their normal state as fast as they are broken up, by the passage of electrons from the rod to the
Earth to the rod, as the case may require. (The Earth must be regarded as containing free electrons and as being able to accommodate many more, without, observably electrified, owing to its great size. Any electrified body, whether charged positively or negatively, immediately becomes neutral when connected with the Earth either directly or through a conductor. ) It appears to be always the electrons that move, and not the positively charged atoms (or 'ions', as they are called). This would be expected, because of the much smaller mass of the electrons. If, however, a conductor be held by an insulating handle, so that electrons cannot pass between it and the hand. It also can be electrified by friction. In all experiments on frictional electricity the apparatus used must be quite dry, otherwise any electrification produced is destroyed, since moisture has conducting properties.

Permanent Magnetism.

The electric current consists simply of electrons or ions traveling round and round a circuit, and it may well be asked why, apart from the general thirst for knowledge, we should be interested to constructing vast machines in order to make invisible particles do the same thing over and over again. Two reasons have already been given: we can use such a process to produce chemical action, as in electrolysis and electroplating, and we can use it to produce light and heat. The third, and the most important reason of all, is that we can use it to produce magnetic force. It has already been said that a circular current acts as a magnet, but before considering the magnetic effects of a current in more detail we must examine the properties of the so-called "permanent" magnets - pieces of iron and steel which attract other pieces of iron and steel without any obvious connection with electricity at all, although, as already stated, we believe the force to be associated with the motion of electrons within the magnets.

Interpretation Of Magnetism.

We assume that an electron moving in an orbit is a small magnet. For simplicity, suppose the orbit is a circle in plane of this sheet of paper, and suppose the electron is revolving in a clockwise direction. Then the upper side of the paper is a S-pole and the lower side is a N-pole. If another similar orbit existed in a parallel plane just above the first, there would therefore be attraction between them and the orbits would approach one another, while if the second electrons were revolving in the opposite direction to the polarity they would be reversed and there would be repulsion. Each atomic electron revolving in its orbit is therefore a small magnet, and the magnetic properties of observable bodies must be expressed in terms of interaction of these intra-atomic magnets. Like the assumption of the existence of elementary particles in atoms, this is not orbitrary guesswork. We can experiment with electrically charged bodies of observable size moving in orbits, and we can find that they do in fact behave as magnets in the manner just described. It is therefore quite reasonable to suppose that the elementary charges behave similarly, and provide us with elements out of which we can build a satisfactory theory of magnetism.

III. Вопросы для зачета и экзамена.

1. Where do you study?
2. What faculty do you study?
3. What can you say about your future speciality?
4. Who is your best friend?
5. Where does your father (mother, sister, brother) work (study)?
6. When does your working day begin?
7. What do you usually do in the morning?
8. What do you have for breakfast (dinner, supper)?
9. How do you get to the University?
10. Till what time are you busy at the University?
11. How do you spend your leisure time?
12. How often do you go to the cinema?
13. What music (books, films) do you like?
14. Do you watch any programs on T. V?
15. What subjects do you study at the University?
16. What is your favorite subject?
17. When and where were you born?
18. Where do you live?
19. Why did you decide to enter the University?
20. When will you be able to speak English fluently?
21. Who is your favorite writer (poet, actor, sportsman)?
22. What books of this writer do you like best?
23. What famous American, British and Uzbek writers do you know?
24. Is your family large or small?
25. How old are your parents?
26. Have you many relatives (aunts, uncles, cousins)?
27. How many seasons are there in the year and what are they?
28. When does it often rain?
29. When do trees begin to burst into leaf?
30. What holiday does our Republic celebrate in spring?
31. How do you spend your time in summer?
32. Do you listen to the latest news every day?
33. What for do you study English?
34. What is your native city?
35. What was the ancient name of Tashkent?
36. What are the friends-sister cities of Tashkent do you know?
37. How many theatres are there in Tashkent? What are they?
38. What places of interest in Tashkent do you know?
39. When was Exhibition Hall opened and where is it situated?
40. What can you tell about the T. V. tower?
41. How many stations are there in Tashkent Underground and when was it opened?
42. What territory does the Republic of Uzbekistan occupy?
43. When did Uzbekistan become independent?
44. What does the independence for our Republic mean?
45. Where is Uzbekistan situated?
46. What is the climate of our Republic?
47. What can you say about the Constitution of our Republic?
48. Who is the President of Uzbekistan now?
49. How is the Supreme Council of Uzbekistan called?
50. What is the official name of Great Britain?
51. What parts does G. B. consist of?
52. What is the capital of G. B. ?
53. What sea separates G. B. from the European continent?
54. What climate has G. B. ?
55. What are the most important parts of London? Speak about each part.
56. Who is the Queen of G. B. ?
57. How is the residence of the Queen called?
58. What places of interest in London do you know?
59. Why do the Englishmen say about monarch's power: "They reign, but don't rule. »
60. What do the Londoners say about their city?
61. Where is the official residence of the Prime Minister of England situated?
62. What is Westminster Abbey?
63. What do you know about the parks of London?
64. What picture gallery is the largest in London?
65. What are the most famous Universities in G. B.?

Литература:

1. Islom Karimov “Building the Future. Uzbekistan – its own model for transition to a market economy”.

2. К. Иванова “English for students of electrical engineering”. Л. 1983.

3. З. Павлова “Сборник общенаучных и технических текстов на английском языке”. М., Высшая школа, 1964.

4. В. М. Макеева “Английский язык” (для неязыковых вузов). М., Высшая школа, 1968.

Содержание.

Пояснения к выполнению контрольных работ …………………………….. 3

Варианты контрольных работ ………………………………………………. 4

Тексты для чтения и перевода ……………………………………………… 10

Вопросы для зачета и экзамена …………………………………………….. 16

Скачали данный реферат: Снетков, Козарь, Бесфамильнов, Lunin, Vanzin, Strelkov, Гансовский, Кривков.
Последние просмотренные рефераты на тему: реклама реферат, реферат на тему развитие, предмет культурологии, сжатое изложение.





Предыдущая страница реферата | 1  2  3  4  5