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V. Get ready to retell Text 1A: write down the key words.
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VI. Do the following grammar exercises:
a) Combine the following sentences using Participle I according to the model:
Model: These scientists study the relations between energy and matter. They are physicists. – These scientists studying the relations between energy and matter are physicists.
1. These scientists study living matter and its processes. They are biologists. 2. These scientists study the multitude of compounds of which matter is comprised. They are chemists. 3. These people study the earth's crust. They are geologists. 4. This material has equal numbers of positive and negative charges in its atoms. It is a conductor. 5. This electric conductor has a conductivity intermediate between that of an insulator and that of a metal. It is a semiconductor.
b) Combine the following sentences according to the model:
Model: Steam does mechanical work. It loses heat energy. –While (when) doing mechanical work, steam loses heat energy.
1. Yablochkov experimented with various materials. He wanted to find some substance glowing in a vacuum. 2. An electric motor does mechanical work. This motor must overcome some force. 3. Motors work in exposed situations. They require enclosure of working parts. 4. Greek philosophers discussed the structure of matter. They called its smallest particles atoms. 5. Ancient Greeks rubbed amber with wool or fur. They noticed that amber could attract light objects.
c) Change the following sentences according to the model:
Model: An insulator is known to contain few free electrons. – It is known that an insulator contains few free electrons.
1. An electric current is known to be a stream of electrons driven through a conductor. 2. The electric current is considered to flow from the negative to the positive terminal. 3. The electrons are said to pass from one atom to another. 4. Different substances are known to differ markedly in electrical conductivity. 5. Every student is supposed to know such fundamental terms as intensity of the current, voltage, electromotive force (e.m.f.), and resistance.
Text 1В
Read and translate the text, using the given vocabulary. Learn the words and word combinations by heart.
Vocabulary
| at rest | в покое |
| in motion | в движении |
| condenser plates | пластины конденсатора |
| to rub | тереть |
| latter | последний (из двух названных) |
| to depend on (upon) | зависеть от |
| permanent magnet | постоянный магнит |
| temporary magnet | электромагнит |
| to magnetize | намагничивать |
| to retain | сохранять |
| compass needle | стрелка компаса |
| magnetic field | магнитное поле |
| horseshoe magnet | подковообразный магнит |
| bar magnet | стержневой магнит |
| north (south) magnetic pole | северный (южный) магнитный полюс |
| inexpensive | недорогой |
| coil | катушка, обмотка |
| magnetic flux / lines of force | силовые линии магнитного поля |
| to be based on | основываться на |
| rotating generator | вращающийся генератор |
Check pronunciation of the following words:
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electrodynamics, molecule, magnetize, permanent, through, flux, either.
Branches of Electricity. Electromagnetism
The study of electricity may be divided into three classes (or branches):
a) magnetism;
b) electrostatics;
c) electrodynamics.
Magnetism is the property of the molecules of ion and other certain substances due to which they store energy in a field because of the arranged movement of the electrons in their atoms.
Electrostatics is the study of electricity at rest, or static electricity. Examples of this type of electricity are charges on condenser plates. Rubbing glass with silk produces static electricity.
Electrodynamics is the study of electricity in motion, or dynamic electricity. The electricity which flows through wires for light and power purposes is a good example of the latter type of electricity.
The principles of magnetism are of great importance in the field of electricity as generators, transformers and motors depend on magnets and magnetism in their operation.
A magnet can be either permanent or temporary. If a piece of iron or steel is magnetized and retains its magnetism, it is a permanent magnet. Permanent magnets are the basis for some of the simpler devices. The compass needle responds to the magnetic field of the Earth which is itself a permanent magnet. Other examples of permanent magnets are a horseshoe magnet, a bar magnet, etc. Each of these magnets has north and south magnetic poles.
Permanent magnets are used for producing the magnetic field necessary for operation of small, inexpensive electrical motors.
When current flows through a coil, a magnetic field with a north and south poles is set up like that of a permanent magnet. However, when the current flow stops, the magnetic field disappears as well. This type of temporary magnetism is called electromagnetism.
When electricity flows through a wire or conductor, magnetic lines of force (magnetic flux) are created around that wire. When a piece of wire is passed through a magnetic field, electricity is created in that wire.
Electromagnetic method of producing electricity is based on operation of rotating generators in which the electricity is produced by conductors moving through a magnetic field. This method is used for generators of various sizes.
Note:
for light and power purposes – для освещения и питания силовых установок.
Exercises
I.Do the following tasks:
1. Match the words to form a phrase:
| permanent | a. plate |
| magnetic | b. generator |
| static | c. magnet |
| rotating | d. pole |
| south | e. electricity |
| condenser | f. field |
b) Complete the sentences, using the phrases from ex.1a:
1. Electrostatics is the study of electricity at rest, or.... 2. The compass needle responds to the magnetic field of the Earth which is itself a.... 3. Examples of static electricity are charges on.... 4. Permanent magnets are used for producing the... necessary for operation of small, inexpensive electrical motors. 5. When current flows through a coil, a magnetic field with a north and a... is set up like that of a permanent magnet.
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II. Answer the questions according to the text content:
1. What classes can the study of electricity be divided into?
2. What helps the molecules of iron to store energy in a field?
3. Can you define electrostatics? Give examples.
4. What is the role of magnetism in the field of electricity?
5. What kinds of magnet do you know?
6. What examples of permanent magnets can you give?
7. What happens to a wire when electricity flows through it?
8. What is the principle of electromagnetic method of producing electricity?
9. Where is electromagnetic method of producing electricity used?
III. Complete the following definitions:
§ Electrodynamics is the study of....
§ Permanent magnet is a piece of iron or steel which....
§ Magnetism is the property of the molecules of iron and other certain substances due to which....
§ Electromagnetism is the type of temporary magnetism when the following happens:....
§ Magnetic flux or magnetic lines of force are created around the wire when....
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