Exercise 17. Choose the best paragraph to answer the question

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1. What does the value of the electric current in a conductor depend on?

a) 2 b) 1

c) 3 d) 4

Exercise 18. Choose the best answer

1. The electric instrument measuring the electric current is connected in parallel to a circuit.

a) it is false b) it is true

c) I don’t know d) there is no information

2. What materials offer the least resistance to the flow of an electric current through them?

a) conductors b) non conductors

c) insulators d) wattmeters

Exercise19. The below-mentioned words all appear in the text C you are going to read:

A). Work with the dictionary and find the transcription and the meaning of the words

B). Practice pronouncing the words

1. bridge for determining inductance – мост для определения индуктивности

2. to join in series (in parallel) – соединять последовательно (параллельно)

3. to assemble a circuit – собирать цепь

4. to adjust to a value – регулировать, настраивать на величину

5. to be equal to – равняться

6. means – средства

Exercise 20. Read the words correctly and guess their meanings. Consult the dictionary

measuring, technique, etc., pressure, value, digital voltmeter, ammeter, bridge, method, to determine inductances, rheostat, in series, adjust, oscillographs

Exercise 21. Read the text C and do exercises after the text

Text C. Laboratory of Electrical Measuring

In the electrical measuring laboratory students get acquainted with measuring technique and its operation rules. They study methods of measuring both electrical values (resistance, current, etc.) and non-electrical ones (t*, pressure, speed, etc.) by electrical means. Various types of modern instruments, such as electronic digital voltmeters, bridges for determining unknown inductances, oscillographs are in wide laboratory use.

The simplest test in the electrical measuring laboratory is the measurement of an unknown resistance by the ammeter-voltmeter method. A rheostat, an ammeter and an unknown resistance are connected in series with the source of d.c. (it may be battery).

A voltmeter is joined in parallel with the elements of the circuit. When the circuit is assembled and checked, the current is switched on and adjusted to a definite value with the help of the rheostat. The ammeter will show the current in the circuit and the voltmeter will show the voltage on an element of the circuit.

According to Ohm’s law resistance is equal to voltage divided by current. Thus, putting the value taken from the instruments into the formula one may calculate the unknown resistance for any given value of current.

Exercise 22. Answer the following questions

1. What do students study in the electrical measuring laboratory? 2. What electrical and non-electrical values do students measure? 3. Various types of modern instruments are in wide laboratory use, aren't they? 4. What are these instruments? 5. Is the measurement of an unknown resistance the simplest test in the electrical measuring laboratory? 6. In what way are a rheostat, an ammeter and an unknown resistance connected with the source of d.c.? 7. Will the ammeter show the current in the circuit? 8. What is resistance equal to according to Ohm's law?

Exercise 23.Translate the sentences into English

1. Простейшим опытом в лаборатории электроизмерений является измерение неизвестного сопротивления. 2. Вольтметр подсоединяется к элементам цепи параллельно. 3. Согласно закону Ома сопротивление равно напряжению, деленному на ток. 4. В лаборатории широко используются осциллографы, электронные цифровые вольтметры и мосты для определения неизвестных индуктивностей. 5. Амперметр показывает ток в цепи, а вольтметр – напряжение на элементах схемы. 6. Ток усиливается на определенную величину с помощью реостата. 7. При известных величинах тока и напряжения на элементе можно подсчитать величину сопротивления. 8. В лаборатории электроизмерений студенты изучают методы измерений как электрических, так и неэлектрических величин.