Методическая разработка урока по профессиональному английскому языку на тему:Measurable parameters. Meters .

Lesson №7

Тема: Measurable parameters. Meters

Цели: Активизировать в речи учащихся использование новой лексики, связанную сизмирительным параметрами.   

Задачи:

1) читать текст с пониманием основного содержания

2) воспринимать текст на слух, добиваясь в случае необходимости понимания с помощью переспроса, уточняющих реплик;

3) повторение лексического материала

Тип урока: Обяснение новой темы

Оборудование: ИКТ, лекция соответствующая содержанию урока

Procedure of the lesson:

Task1. Translate into Russian:

1. One should take into consideration the difference between these circuits.

2. One should take into consideration that the ammeter is connected to the circuit in series.

3. What should one take into consideration using the ohmmeter?

Text: Meters

Any instrument which measures electrical values is called a meter. Among the most common meters used there are the ohmmeter, the ammeter and the voltmeter.
An ammeter measures the current in amperes. The unit is named after Andre Marie Ampere, a French scientist, who discovered a great number of facts about electricity over a hundred years ago. The abbreviation for the ampere is amp. A voltmeter measures the voltage and the potential difference in volts. The volt is named after Alessandro Volta, an Italian scientist.
 

The current in a conductor is determined by two things, the voltage across the conductor and the resistance of the conductor. Every material object offers some resistance to the flow of an electron current through it. Good conductors like the metals, copper, silver and aluminum offer very little resistance, while nonconductors such as glass, wood and paper offer a very high resistance.

The unit by which resistance is measured is called the ohm. The resistance in practice is measured with the ohmmeter.

The ohmmeter is used to measure the value of resistance. It consists of а milliammeter calibrated to read in ohms, а battery and resistors. The meter is connected in parallel and the circuit is not opened when its resistance is measured.

The readings on the scale show the measured value. The ammeter is used to measure the value of current. When the ammeter is used the circuit should be opened at one point and the terminals of the meter should be connected to it. One should take into consideration that the positive terminal of the meter is connected to the positive terminal of the source; the negative terminal to the negative terminal of the source. The ammeter should be connected in series. The readings on the scale show the measured value.

A wattmeter measures electrical power in watts. Very delicate ammeters are often used for measuring very small currents. A meter whose scale is calibrated to read a thousandth of an ampere is called a milliammeter. One whose scale is calibrated in millionth of an ampere is called a micro ammeter or galvanometer.
Whenever an ammeter or voltmeter is connected to a circuit to measure electric current or potential difference the ammeter must be connected in series and the voltmeter in parallel.

Fig. 11. Circuit diagram showing the connections for an ammeter and voltmeter.

As illustrated in Fig. 11, the ammeter is so connected that all of the electron current passes through it. To prevent a change in the electron current when such an insertion is made, all ammeters must have a low resistance. Most ammeters therefore have a low resistance wire, called a shunt, connected across the armature coil. A voltmeter, on the other hand, is connected across that part of the circuit for which a measurement of the potential difference is required. If the 'potential difference between the ends of the resistance R is wanted, the voltmeter is connected as shown.

Vocabulary:

meter- измерительный прибор

battery- батарея

scale- шкала

readings- показания на шкале (прибора)

terminal- клемма

positive- положительный

negative- отрицательный

to measure- измерять

to take into- consideration принимать во внимание

in this way- таким путем, таким образом

Task 2. Pair work. Put these questions to your groupmate. Let him/her answer them.

1. What is the ammeter used for?

2. What is the voltmeter used for?

3. How is a voltmeter connected to the circuit?

4. What meter do we connect to the circuit in series?

5. Why must an ammeter have a low resistance?

6. What is the ohmmeter used for?
7. What terminals does а meter have?

8. Across what part of the circuit is a voltmeter connected?
9. Should the measured circuit be opened when the voltmeter is used?

10. Should the measured circuit be opened when the ammeter is used?

11. In what way should the voltmeter be connected to the circuit?

12. In what way should the ammeter be connected to the circuit?

13. What instruments are used to measure an electric current and potential difference?

14. What is the difference between а voltmeter and an ammeter?

15.What common meters are used to measure the values in а circuit?
Task 3. Complete the sentences using the correct variant:

1. The ammeter is
а) а common meter. b) an uncommon meter.

2. In order to measure the value of current
а) the ohmmeter is used. b) the voltmeter is used. с) the ammeter is used.
3. А meter has
а) positive terminals only. b) negative terminals only. с) positive and negative terminals.

4. When the ammeter is used
а) the circuit should be opened. b) the circuit should not be opened.

5. The ammeter should be connected
а) in series. b) in parallel.

6. One should take into consideration that
а) the positive terminal should be connected to the negative terminal. b) the positive terminal should be connected to the positive terminal of the source.
Task 4. Complete these sentences using while. Follow the model.
Model: The ammeter is used to measure the value of current ... The ammeter is used to measure the value of current while the ohmmeter is used to measure the value of resistance.

1. The ohmmeter is used to measure the value of resistance ...

2. The ammeter is connected in series ...

3. When the ammeter is used to measure the value of current the circuit should be opened ...
Task 5. Solve the following problems:

1. Suppose the ammeter scale reads 1.9 amp, the voltmeter scale reads

2.4 V; how much is the value of resistance in the measured circuit?

2. Suppose the ohmmeter scale reads 75 ohms, the voltmeter scale reads 220 V; how much is the value of current in the measured circuit?

3. Suppose that you have а series circuit consisting of three resistors and а voltage source. R1=O.18 ohm, R2 =1.15 ohms, R3=2 ohms, I = 1О amp. Find the voltage drop across each resistor; find the value of voltage in the circuit. Suppose R1 gets open. What does it result in?

4. Two resistors are connected in series. R1 = 7,000, R2 = 2,200, I = 110 amp. Find the voltage drop across each resistor. Suppose no current passes through the circuit, what does it result from?
Task 5. Translate measurement instruments according to the picture:

33 - индикатор;

34 - глубиномер;

35 - микрометр;

36 - калиберная пробка;

37 - угломер;

38 - универсальный угломер;

39 - калиберная плитка;

40 -упорный угольник;

41 - предельная скоба;

42 - щуп;

43 - стальная метрическая линейка

Task 6. Open the brackets using the right form of adjectives:

1. Winter is (cold) season of the year. 2. Moscow is (large) than St. Petersburg. 3. Which is (long) day of the year? 4. The Alps are (high) mountains in Europe. 5. Even (long) day has an end. 6. It is one of (important) questions of our conference. 7. Your English is (good) now. 8. Who knows him (well) than you? 9. We have (little) interest in this work than you. 10. Health is (good) than wealth. 11. Your son worked (well) of all. 12. Today you worked (slowly) than usually.

Task 7. Translate the sentences:

1. This book is not so interesting as that one. 2. The Baltic Sea is not so warm as the Black Sea. 3. The more you read, the more you know. 4. My brother is not as tall as you are. 5. The earlier you get up, the more you can do. 6. Today the wind is as strong as it was yesterday. 7. Your room is as light as mine. 8. John knows Russian as well as English. 9. Mary is not so lazy as her brother. 10. The longer the night is, the shorter the day. 11. The less people think, the more they talk.

Text p.26 Ex.3 p.27