Words and word combinations to be remembered

pick up – поднимать, подбирать	electric circuit – электрическая цепь	battery – батарея, аккумулятор
to be directed – быть направленным	flow – поток	wire – проволока
consume – потреблять	electric field – электрическое поле	device – устройство
supply – снабжать, заменять	household appliances – бытовые электроприборы	charged – заряженный
force – заставлять, вынуждать	terminal – клемма	rate – уровень

Ex. 1. Translate from Russian into English:

Электрическая цепь, электрические приборы, электрический заряд, электрическое поле, ампер, статическое электричество, электрический звонок, механическая энергия, клемма, аккумулятор, измерять в вольтах, действовать на расстоянии, нагревать проволоку, переходить в другую форму, потреблять энергию.

Ex. 2. Make up the word combinations using the words from 2 columns, make up some sentences with these word combinations:

a measure	a battery
to measure	a current
electric	of strength
to force	of electricity
charge	force
to charge	the length

Ex. 3. Fill in the blanks:

1. The flow of charge through wires allows us to… .

2. Electric force is described as … .

3. A charged balloon can have an attractive affect upon an oppositely charged balloon even when … .

4. The electric force acts … .

5. A charged object creates … .

6. The electric field direction about a positive source charge is always directed away from … .

7. The electric field direction about a negative source charge is always directed toward … .

8. The standard metric unit for current is … .

9. The mere movement of charge from terminal to terminal is of little use if the electrical energy possessed by the charge … .

10. When a circuit is equipped with a light bulb, electric bell, or motor, the electrical energy supplied to the charge by the battery is transformed ... .

Ex. 4. Answer the following questions:

1. What does the word “electricity” come from? 2. What does the flow of charge through wires allow us? 3. Electric force is described as a non-contact force. What does it mean? 4. What is the standard metric unit for current? 5. What is the standard metric unit for electrical force? 6. What is a short circuit? 7. When is electrical energy transformed into other forms? 8. What kind of energy can electrical energy be transformed into? 9. What voltage are most household appliances built for? 10. What is static electricity?

Ex. 5. Say a few words about:

• discovery of electricity

• electrical field

• terms everyone needs to know in buying and using electric appliances

• the transformation of energy in electrical circuits

Unit 9. Waves

Waves are everywhere. Sound waves, visible light waves, radio waves, microwaves, water waves, sine waves, cosine waves, stadium waves, earthquake waves, waves on a string are just a few of the examples of our daily encounters with waves.

A transverse wave is a wave in which the particles of the medium are displaced in a direction perpendicular to the direction of energy transport. A transverse wave can be created in a rope if the rope is stretched out horizontally and the end is vibrated back-and-forth in a vertical direction.

The dashed line drawn through the center of the diagram represents the rest position of the string. This is the position that the string would assume if there were no disturbance moving through it. Once a disturbance is introduced into the string, the particles of the string begin to vibrate upwards and downwards. At any given moment in time, a particle on the medium could be above or below the rest position. Points A, E and H on the diagram represent the crests of this wave. Points C and J on the diagram represent the troughs of this wave.

The wave shown above can be described by a variety of properties. One such property is amplitude. The amplitude of a wave refers to the maximum amount of displacement of a particle on the medium from its rest position. In a sense, the amplitude is the distance from rest to crest. Similarly, the amplitude can be measured from the rest position to the trough position.

The wavelength of a wave is simply the length of one complete wave cycle. A wave is a repeating pattern. It repeats itself in a periodic and regular fashion over both time and space. And the length of one such spatial repetition (known as a wave cycle) is the wavelength. 

Alongitudinal wave is a wave in which the particles of the medium are displaced in a direction parallel to the direction of energy transport. A longitudinal wave can be created in a slinky if the slinky is stretched out horizontally and the end coil is vibrated back-and-forth in a horizontal direction. If a snapshot of such a longitudinal wave could be taken so as tofreeze the shape of the slinky in time, then it would look like the following diagram.

Because the coils of the slinky are vibrating longitudinally, there are regions where they become pressed together and other regions where they are spread apart. A region where the coils are pressed together in a small amount of space is known as a compression. A compression is a point on a medium through which a longitudinal wave is travelling that has the maximum density. A region where the coils are spread apart, thus maximizing the distance between coils, is known as a rarefaction. A rarefaction is a point on a medium through which a longitudinal wave is travelling that has the minimum density.

There are two most common types of waves – sound waves and light waves.

Are there any differences between them? The physical difference, of course, is that light waves are due to varying electric and magnetic forces, while sound waves are due to vibrating layers or particles of the medium concerned. Light can travel trough a vacuum, but sound cannot travel trough a vacuum. Another very important difference is that the vibrations of the particles in sound waves are in the same direction as that along which the sound travels, whereas the vibrations in light waves are perpendicular to the direction along which the light travels. Sound waves are therefore longitudinal waves, whereas light waves are transverse waves. Sound waves can be reflected and refracted, and can give rise to interference phenomena; but no polarization phenomena can be obtained with sound waves since they are longitudinal waves, unlike the case of light waves.