Translate the following sentences paying special attention to the words in bold.

1. The faster the molecules of substance move, the higher is the temperature of the substance.

2. The large the water pipe, the more water passes through it.

3. The more you read, the more you learn.

4. The shorter the wire, the less is its resistance to current flow.

5. The greater the number of free electrons in a substance, the better that substance conducts electricity.

 

Fill in the blanks with the following words and expressions: as, as well, as well as.

1. It is necessary to remember the term “circuit” … it is almost impossible to work with electricity without working with circuits.

2. Copper wires are mostly used … conductors of electricity.

3. A “short” may cause wire fault … cable fault.

4. In addition to travelling through solids, the electric current can flow through liquids and gases ….

5. … a cold object and a hot one are brought into contact, the former gets warmer and the latter gets colder.

6. … a conductor becomes warmer, it is unable to pass electric charges as freely as it did before its temperature began to rise.

7. The magnitude of the current … the voltage and resistance may vary from a minute amount to a very large quantity.

 

8. Fill in the blanks with suitable prepositions if necessary and make up sentences with the following infinitives.

To answer …; to apply …; to be interested …; to contribute …; to consist …; to depend …; to invite …; to pay attention …; to play a part …; to go …; to be followed ….

 

Translate the following sentences.

1. Я не могу не ответить на этот вопрос.

2. Он не может не упомянуть об этом.

3. Мы не могли не вспомнить о пожаре, вызванном коротким замыканием.

4. Она не может не думать о своей исследовательской работе.

5. Я не могу не знать, что короткое замыкание может вызвать повреждение провода.

 

Speak on:

1. The properties of the electric circuit.

2. The conductors of electricity.

3. The insulators of electricity.

UNIT 11

Potential difference, electromotive force and resistance

Vocabulary

free – несвязанный электрон, свободный электрон	electromotive force (emf) |ɪˌlɛktrəˈməʊtɪv fɔːs| – электродвижущая сила
excess|ɪkˈsɛs|– избыток,превышение	potential difference |pə(ʊ)ˈtɛnʃ(ə)l ˈdɪf(ə)r(ə)ns| – разница потенциалов
deficiency|dɪˈfɪʃ(ə)nsi|– отсутствие, нехватка	provided |prəˈvʌɪdɪd| – при условии
manner|ˈmanə| – способ, метод, образ	to suspend |səˈspɛnd| – подвешивать

 

The amount of electrons at a point is known as the potential at that point. As was previously stated, there is always a disorderly movement of free electrons within all substances, especially metals. Thus, if at one end of a conductor there is an excess of electrons and at the other end – a deficiency, the excess of electrons will flow in a disorderly manner towards the point of deficiency. It is the difference of potential that causes the free electrons to flow from one point of the conductor to another. Of course, the greater the difference, the greater is the flow.

Let us suppose that there is a movement of electrons through the wire, say, from point A to point B! What does it mean? It means that there is an excess of electrons at point A. Unless there were a flow of electric current between A and B in any direction, it would mean that both the former and the latter were at the same potential.

The electromotive force is the very force that makes the electrons move along a conductor, the letters emf standing for the above term. In effect, it is the emf that moves electrical charges from one point in an electric circuit towards another. In case this emf is direct, the current, too, is direct. On the other hand, were the electromotive force alternating, the current would be alternating too.

One need not explain to the reader that a current is unable to flow in a circuit consisting of metallic wires without a source of emf. The source under consideration may be a cell or a battery, a generator, a thermocouple or a photo cell, etc. Needless to say, the emf is measurable and it is the volt that is the unit to be used for measuring it.

In addition to electromotive force and potential difference reference should be made here to another important factor that greatly influences electrical flow, namely, resistance. So, to resistance shall we turn our attention now. The reader most probably remembers that all substances offer a certain amount of position, that is to say resistance, to the passage of current. This resistance may be high or low depending on the type of circuit and the material employed. Take glass and rubber as an example! They offer a very high resistance and, hence, are considered to be good insulators. Nevertheless, one must not forget, too, that all substances do allow the passage of some current, provided the potential difference is high enough.