A) Cover the right column and read the English words. Translate them into Russian and check your translation

Meters

4.

3.

Series Circuit and Parallel Circuit

B) Cover the left column and translate the Russian words back into English.

A) Cover the right column and read the English words. Translate them into Russian and check your translation.

branch	[bra:ntfl
line
value	[Vaelju]
voltage drop
series	['siariiz]
parallel	['рэегэЫ]
main	[mem]
to use	(ju:z]
in order (to)

отвод

линия

величина

падение напряжения

последовательное

параллельное

главный, основной

использовать

для того чтобы

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-.11-

3. In a parallel circuit a trouble a) in one branch b)

4. No current in a parallel cir- a) cuit b)

5. The sum of IR voltage drops a) b) c)

Compare circuits a and b. Circuit a consists of a voltage source and two resistors. The resistors are connected in series. Circuit a is a series circuit.

Circuit b consists of a voltage source and two resistors. The resistors are connected in parallel. Circuit b is a parallel circuit.

л, 4ZZJ-

A parallel circuit has the main line and parallel branches.

a

In circuit b the value of voltage in R_t \ equals the value of voltage in R₂. The value of voltage is the same in all the ele­ments of a parallel circuit while the value of current is different. A parallel circuit is J used in order to have the same value of voltage.

In circuit a the value of current in Rj
_R equals the value of current in R₂. The

-CXD--- 1 value of current is the same in all the ele-

ments of a series circuit while the value of voltage is different. A series circuit is used

j |_z---------- 1 _m order to have the same value of current.

^

Fig.2

In R\, Vi=IRi is the voltage drop in R\. In Ri the voltage equals IxR₂; IR₂ is the volt­age drop in Ri. In circuit с a trouble in one element results in no current in the whole circuit. In circuit d a trouble in one branch results in no current in that branch only, a trouble in the main line results in no cur­rent in the whole circuit.

2. Complete these sentences using the correct variant:

1. A parallel circuit has

a) parallel branches only.

b) the main line and parallel branches.

2. A parallel circuit is used in a) to have the same value of current in
order all the elements.

b) to have the same value of voltage in all the elements.

results in no current in that branch only.

results in no trouble in the whole cir­cuit.

results from a trouble in one branch, results from a trouble in the main line.

equals the value of voltage in the cir­cuit.

is less than the smallest voltage drop, is more than the value of voltage in the circuit.

Complete the sentences using while. Follow the model:

Model: Resistors connected in series have the same value of current... Resistors connected in series have the same value of current while resistors connected in parallel have the same value of voltage.

1. Resistors connected in series have different values of voltage while....

2. A trouble in one element of a series circuit results in no current in the whole circuit while....

3. In order to have the same value of current in all the elements, a series circuit is used while....

4. No current in a parallel circuit results from a trouble in the main line while....

Answer the following questions:

1. What type of circuit has the main line and parallel branches?

2. What type of circuit is used in order to have the same value of current in all the elements?

3. What type of circuit is used in order to have the same value of voltage in all the elements?

4. What does a trouble in the main line result in?

5. What does a trouble in a branch result in?

6. What does no current in a series circuit result from?

7. How much does the sum of IR voltage drops equal?

8. What is the difference between series and parallel circuits?

Pair work. Ask your groupmate to draw and describe a series-parallel circuit.

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-13-

k>^

1. a) Cover the right column and read the English words. Translate them into Russian and check your translation.

b) Cover the left column and translate the Russian words back into English.

meter battery scale readings terminal positive negative to measure to take into consideration in this way

['mite] f'baetan] [skeil] [temml] ['pozitiv] ['negativ] ['тезэ]

измерительный прибор

батарея

шкала

показания на шкале (прибора)

клемма

положительный

отрицательный

измерять

принимать во внимание

wei

таким путем, таким образом

2. Translate into Russian (see page 98):

1. One should take into consideration the difference between these cir-

cuits.

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?

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 milliammeter 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.

Fig.3

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

I H

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.

Fig. 4

1. The ammeter is 2. In order to measure the value of current 3. A meter has 4. When the ammeter is used

3. Complete the sentences using the correct variant:

a) a common meter.

b) an uncommon meter.

a) the ohmmeter is used.

b) the voltmeter is used.

c) the ammeter is used.

a) positive terminals only.

b) negative terminals only.

c) positive and negative terminals.

a) the circuit should be opened.

b) the circuit should not be opened.

5. The ammeter should be con- a) in series, nected b) in parallel.

6. One should take into consid- a) the positive terminal should be con-eration that nected to the negative terminal.

b) the positive terminal should be con-• nected to the positive terminal of the source.

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

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5. 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. What is the ohmmeter used for?

4. What terminals does a meter have?

5. Should the measured circuit be opened when the voltmeter is used?

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

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

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

9. What is the difference between a voltmeter and an ammeter?

10. What common meters are used to measure the values in a circuit?

6. 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 Rj gets open. What does it result in?

4. Two resistors are connected in series. Ri = 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?

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