Английский язык в текстах и упражнениях для электромеханических специальностей среднего профессионального образования (стр. 2 )

a) results from a trouble in one branch

b) results from a trouble in the main line

5. the sum of IR voltage drops

a) is equal to the value of voltage in the circuit

b) is less than the smallest voltage drop

c) is more than the value of voltage in the circuit

B

Finish the sentences using the words with the opposite meaning.

M o d e 1: 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....

C

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 is the sum of IR voltage drops equal to? 8. What is the difference between series and parallel circuits?

Ответы и решения

А

1-b; 2-b; 3-a; 4-b; 5-a.

В

1.  in parallel.......... the same

2.  parallel.............. in that element only

3.  voltage................ parallel

4.  series.................. in one element.

С

1.  parallel

2.  series

3.  parallel

4.  no current in the whole circuit

5.  no current in that branch

6.  an open or a short

7.  the value of voltage in the circuit

8.  the resistors are connected in series; .. .in parallel.

Lesson 3
An Open in a Parallel Circuit
any	light
since	bulb
'operate	advantage

An open in any circuit results in no current. In parallel circuits there is a difference between an open in the main line and an open in a branch: an open in the main line of a circuit of this type results in no current in the whole circuit while an open in a parallel branch results in no current in that branch only.

Let us take 2 parallel circuits "a" and "b" and compare them. Circuit "a" and circuit "b" are used to light bulbs. The first circuit consists of the main line and three parallel branches. No bulb connected across this circuit can light since it has an open in the main line.

Circuit "b" consists of the same elements as the circuit a". It has an open — not in the main line but in one of the branches. Since the open branch has no current, a bulb connected across it cannot light. In all the other branches current passes, since each branch is connected to the voltage source. Bulbs connected across these branches can light. This shows the advantage of a parallel circuit, since an open in one element opens only one branch while all the other branches can operate.

Разрыв в параллельной цепи

Разрыв в любой цепи приводит к отсутствию тока. В параллельных цепях есть разница между разрывом в главной линии и разрывом в ветви: разрыв в главной линии цепи такого типа приводит к отсутствию тока во всей цепи, в то время как разрыв в параллельной ветви приводит к отсутствию тока только в этой ветви.

Возьмем 2 параллельные цепи «a» и «b» и сравним их. Цепь «а» и цепь «b» используются для включения ламп. Первая цепь состоит из главной линии и трех параллельных ветвей. Ни одна лампа в этой цепи не может загореться, если есть разрыв в главной линии.

Цепь «b» состоит из тех же элементов, что и цепь «а». Она имеет разрыв – не в главной линии, а в одной из ветвей. Поскольку в разорванной ветви нет тока, лампа, соединенная с ней, не может загореться. Во всех остальных ветвях ток есть, т. к. каждая ветвь соединена с источником питания. Лампы, соединенные с этими ветвями, могут гореть. Это показывает преимущество параллельной цепи, т. к. разрыв в одном элементе разрывает только одну ветвь, в то время как все остальные ветви могут работать.

EXERCISES

A

Answer the following questions:

1. Why can circuit "b" operate? 2. What does no current

in circuit "a" result from? 3. What is the advantage of a parallel circuit?

B

Solve the following problems:

ppose that you have a series circuit consisting of three resistors and a voltage source. R1= 0.18 ohm, R2 =1.15 ohm, R3 = 2 ohms, I = 10 amp. Find the voltage drop across each resistor; find the value of voltage in the ppose R1 gets open. What does it result in?

2. Two resistors are connected in series. R1 = 7,000 ohms, R2 = 2,200 ohms, I = 110 amp. Find the voltage drop across each ppose no current passes through the circuit, what does it result from?

Ответы и решения

A

1.  an open in one element opens only one branch

2.  all the other branches can operate.

В

1.V1 =0.18x10= 1.8V; V2= 1.15 x 10= 11.5V; V3 = 2 x 10 = 20V. V= 1.8 + 11.5 + 20 =

=33.5V V = 31.5V.

2. VI = 7,000 x 110 = 770,000V; V2 = 2,200 x 110 = 242,000V. An open or a short.

Lesson 4
METERS
meter	One
Battery	Common
Scale	should
readings	measure

The most common meters used 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. 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.

Измерительные приборы

Самые обычные измерительные приборы – это омметр, амперметр и вольтметр. Омметр используется для измерения величины сопротивления. Он состоит из миллиамперметра, откалиброванного в омах, аккумулятора и сопротивлений. Прибор подсоединяется параллельно, и цепь не разорвана, когда меряется ее сопротивление. Показания на шкале показывают измеряемую величину.

Амперметр используется для измерения величины тока. При использовании амперметра цепь надо разорвать в одной точке и соединить ее с клеммами прибора. Надо учитывать, что положительный терминал прибора соединяется с положительным терминалом источника, а отрицательный терминал – с отрицательным терминалом источника. Амперметр надо присоединять последовательно. Показания на шкале показывают измеряемую величину.

EXERCISES

A

Find the correct variant. Remember it:

1. the ammeter is

a) a common meter

b) an uncommon meter

2. in order to measure the value of current

a) the ohmmeter is used

b) the voltmeter is used

c) the ammeter is used

3. a meter has

a) positive terminals only

b) negative terminals only

c) positive and negative terminals

4. when the ammeter is used

a) the circuit should be opened

b) the circuit should not be opened

5. the ammeter should be connected

a) in series

b) in parallel

6.one should take into consideration that

a) the positive terminal should be connected to the negative

terminal

b) the positive terminal should be connected to the positive

terminal of the source

B

Finish the sentences using the words with the opposite meaning:

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

C

Answer the following questions

I. What is the ammeter used for? 2. What is the voltmeter used for? 3. What is the ohmmeter used for? 4. What terminals has a meter? 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?

D

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 voltmeterscale reads 220 V; how much is the value of current in the measured circuit?

Ответы и решения

A

1-a; 2-е; 3-е; 4-a; 5-a; 6-b.

В

1.  the ammeter.................. current.

2. the ohmmeter............. parallel.

3. the ohmmeter............. resistance... .is not opened.

С

1. to measure the value of current

2......................................... voltage

3......................................... resistance

4.  positive and negative

5.  -

6.  yes

7.  -

8.  in series

9.  -

10.  the ohmmeter, the ammeter, the voltmeter.