VII. Solve these problems:

1. How much is the current in the circuit if a 60-volt source is connected

to a resistance of 1,600 ohms?

2. How much is the voltage in a circuit having a current equal to 25 amp,

if a 25-ohm resistance is connected to it?

3. A 70.35-ohm resistance is connected to the circuit. How much is the

voltage if the current equals 4.5 amp?

VIII. Pair work. Ask your group mate to compare circuits a and b (see Fig.1)

1. What do they have in common?

2. Which of the circuits has a trouble?

3. What does the trouble result from?

4. What does it result in?

IX. Answer the following questions:

1. What elements does a circuit consist of?

2. What is the function of a voltage source?

3. What is the function of a conductor?

4. What is the function of a resistor?

5. When is there no current in a circuit?

6. What does an open or a short result in?

Практическая работа № 6 meters

Цели: Введение и активизация в речи лексики по теме «Измерительные приборы».

Оборудование: комплект тестов, раздаточный материал.

Vocabulary

I. Learn the words and expressions.

Meter

Batter

Scale Readings

Terminal

Positive

Negative

To measure to take into

consideration

in this way

измерительный прибор

батарея

шкала

показания на шкале (прибора)

клемма

положительный

отрицательный

измерять

II. Read and translate the text.

Among the most common meters used there are the ohmmeter, the ammeter and the voltme­ter. The ohmmeter is used to measure the value of resistance. It consists of a millimeter cali­brated to read in ohms, a 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.

III. Find English equivalents.

Клемма, батарея, положительный, отрицательный, шкала, измерять, среди, вольтметр, резистор, омметр.

IV. Add necessary letters.

Meas-re, vol-metr, o-m-etr, bat-ery, resis-ance, com-on, am-etr, mil-im-tr, par-aller.

V. Finish the sentences.

1. The ohmmeter is used……..

2. The meter is connected……..

3. The ammeter is used to…………..

4. When the ammeter is used………

5. One should take into………..

VI. Make up the sentences.

1. Ohmmeter, the, most, used, common, there, meters, the, the, ammeter, are, and, the, voltme­ter, among

2. Measure the resistance used to value ohmmeter the of is.

3. Opened is the c in and circuit is when not parallel its is measured resistance meter the connected.

4. The current is of to value ammeter used the measure.

5. The be in connected ammeter series should

VII. 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 a series circuit consisting of three resistors and a voltage source. Ri = 0.18 ohm, R₂= 1.15 ohms, R₃ = 2 ohms, 1=10 amp. Find the voltage drop across each resistor; find the value of voltage in the circuit. Suppose Rx gets open. What does it result in?

4. Two resistors are connected in series. R] = 7,000, R₂ = 2,200, 1 = 110 amp. Find the voltage drop across each resistor. Suppose no current passes through the circuit, what does it result from?