Lesson 4

To behave – вести себя like – подобно , подобный, нравиться

To surround – окружать quantity – количество, величина

Dissimilar – неодинаковый to lose (lost-lost) –терять

Excess – избыток e.m.f. (electromotive force) – электродвижущая сила

Per unit – за единицу d.c. (direct current) – постоянный ток

To cause – вызывать, причинять a.c. (alternating current) – переменный ток

To reverse – менять направление strenght – сила , напряженность, сопротивление

To represent – представлять unidirectional – однонаправленный

Rate – скорость, темп, turn – виток , оборот,

Text 4 electricity

Rubbing a piece of amber the Greek philosopher Thales noticed the effect of attraction of light objects. Today we know that very many substances which we rub behave like amber. We also know that if we rub two dissimilar substances we shall electrify them and they will attract each other. There will be no electrical effect if you rub two similar substances. It is well-known. Modern science knows that an atom is an electrical system. Every electrical system has a nucleus containing positively charged particles. Electrons surrounding the nucleus are negatively charged units. So, any atom consists of electrically charged particles. As the atom having equal amounts of both charges is neutral it produces no electrical effects. If the number of negative charges is unlike the number of positive charges, the atom will produce an electrical effect. Losing some of its electrons the atom has a positive charge, having an excess of electrons it has a negative charge. The electric current is a quantity of electrons flowing in a circuit per unit of time. The electrons move along the circuit because the e. m. f. drives them. A stream of electrons in a circuit will develop a magnetic field around the conductor along which the electrons move. The strength of the magnetic field depends upon the current strength along the conductor. The direction of the field depends on that of the current flow. If the force causing the electron flow is unidirectional, the current is direct (d. c.). If the force causing and changing the electron flow is periodical, the current is alternating (a. c.). When flowing through a conductor the alternating current reverses its direction at regular intervals. The unit measuring the current is the ampere. The ampere is the practical unit representing the rate of flow of electricity. The ampere is simply a measure of the number of electrons passing a given point in a second of time. An ammeter is an electron flow-indicating device. The magnetizing effect of a current depends on the strength of the current and on the number of turns through which the current flows.

Exercises

I. Answer the following questions:

1. What do you know about the substances if to rub them?

2. What do all the atoms consist of?

3. When do we say that the atom is neutral?

4. When will the atom produce an electrical effect?

5. What makes the electrons move?

6. When is the atom either positively or negatively charged?

7. What does the strength of the magnetic field depend upon?

8. Does the direction of the magnetic field depend on that of the current flow?

9. What do we call the direct (alternating) current?

10. What is the ampere?

11. What does the magnetizing effect of a current depend on?

12. What is an ammeter?

II. Give Russian equivalents to the groups of words of the same root:

to electrify — electrical — electrically — electrifying — electrified -electrification;

to indicate - - indicator — indication - - indicating - - indicated - indicative;

magnet — magnetic - to magnetize,

to direct –director - direction— directing — directed — directional - unidirectional — direct current — indirect — directly — indirectly — directive,-

to conduct — conducting — conducted — conduction — conductor non-conductor — conductivity.