II. LESSON 2. An Electric Circuit and Its Properties

 

1. Read and memorize the following words and combinations:

advantage - преимущество

disadvantage - недостаток

appliance - устройство, прибор

area - площадь

cross-sectional area - площадь поперечного сечения

circular mil area - площадь, равная круговому милу

to attach - прикреплять к

automatic line controls - автоматическое управление линии

circle - круг

circuit - цепь, контур, схема

alternating circuit (a-c circuit) - сеть переменного тока

circuit breakers - выключатели в цепи

combination circuit - комбинированная цепь

direct-current circuit (d-c circuit) - цепь постоянного тока

parallel circuit - цепь с параллельным соединением

series circuit - цепь с последовательным соединением

to complete the circuit - замкнуть цепь

to open the circuit - разомкнуть цепь

coefficient - коэффициент

conductor - проводник

poor conductor - плохой проводник

control - управление

cross-section - поперечное сечение

current - ток

alternating current - переменный ток

branch current - ток на одном участке цепи

direct current - постоянный ток

total line current - суммарный линейный ток

decrease - уменьшение

to decrease - уменьшать(ся)

dielectric - диэлектрический

electrical - электрический

electricity - электричество

electron - электрон

to emit - испускать

essential - существенный

to feed - питать

figure - рисунок, цифра, чертеж

flow - поток

frequency - частота

fuse - предохранитель

cartridge-type fuse (fusetron) - патронный предохранитель

gauge - калиброметр

increase - увеличение, возрастание

to increase - увеличиваться, возрастать

insulation - изоляция

insulator - изолятор

length - длина

materials - материалы

to mean (by) - иметь в виду, подразумевать

to minimize - сводить к минимуму

movement - движение

number - количество, число

power - энергия, мощность

source of power - источник энергии

physical - физический

point - точка

starting point - отправная точка

resistance - сопротивление

specific resistance - удельное сопротивление

to resist, to oppose - сопротивляться, противостоять

resistor - сопротивление (прибор)

fixed resistor - постоянный резистор

metallic resistor - металлический резистор

wire-wound resistor - проволочный резистор

variable resistor - регулируемый резистор

rheostat, varistor - реостат

size - размер

sliding contact arm - рычаг со скользящим контактом

strength - прочность, сила

structure - строение, структура

substance - вещество

supply - снабжение, питание

power supply - энергоснабжение

to supply - снабжать, поставлять, питать

temperature - температура

terminals - зажимы, клеммы

to transmit - передавать

value - величина

to vary - изменять, видоизменять

various - разнообразный

voltage - напряжение

applied voltage - приложенное напряжение

nominal rated voltage - номинальное напряжение

voltage drop - падение напряжения

wire - проволока

wiring - проводка

 

2. Read and translate the following text:

ELECTRIC CIRCUIT

An electric circuit is the path taken by an electric current from its source, through the conductors and back to its starting point. The essential parts of any electric circuit are the source of power, the conductors used to transmit the electric current, and the appliance or appliances to be supplied with electrical energy. There are four ways in which electrical appliances may be connected: (1) simple circuit, (2) series circuit, (3) parallel circuit, (4) combination circuit.

A simple circuit is one in which a single resistance is connected across a power source. A series circuit is one in which two or more resistances are connected in one continuous path so that the current passes in turn from one to another. Series circuits are used in radio, television, and other electronic equipment. When two or more resistances are connected so that the current will have two or more paths in which it may flow, it is a parallel circuit. Parallel circuits are used wherever a constant voltage power supply system is needed. House wiring is a good example of the use of this type of circuit.

When a circuit contains both series and parallel circuits, it is a combination circuit. Combination circuits may be connected in series-parallel or parallel-series. When groups of parallel circuits are connected in series, it is called a series-parallel. When groups of series are connected in parallel, it is called a parallel-series circuit. Combination circuits have the advantages of both series and parallel circuits and minimize their disadvantages. Combination circuits are used whenever various types of circuits must be fed from the same power supply.

Electric circuits possess certain properties which influence the flow of electricity in the circuit. They are:

(a) Resistance – a property of a circuit which opposes the flow of electricity. The electrical energy expended in overcoming this reaction is converted into heat. Resistance is manifested whether the current is steady (d. c.), pulsating or alternating. In its effect, resistance can be compared to the friction of water flowing in a pipe.

(b) Inductance – a property which also opposes the flow of electricity but in a different manner from resistance. By virtue of the inductance of a circuit carrying a varying current, an electromotive force is generated in the circuit in such a direction as to oppose the change.

The inductance of a circuit is therefore of importance only where the current is changing. In its effect, inductance may be compared to the inertia of water flowing in a pipe or to the inertia of a rotating mass, such as a flywheel.

(c) Capacitance – a property by virtue of which an electric circuit has the ability to store electricity. This effect is of importance only when the voltage of the system is pulsating or alternating. In its effect, capacitance is similar to the action of a spring which is compressed and released.

 

3. Find the English equivalents in the text:

электрическая цепь, проводник, источник энергии, цепь с последовательным соединением, цепь с параллельным соединением, простая цепь, передавать электрический ток, снабжаться электрической энергией, электрические устройства, отправная точка, уменьшить сопротивление, проволочный резистор, уменьшить недостатки, соединяться параллельно, сопротивление, индуктивность, емкость, преобразовываться в тепло, поток электричества, быть важным, маховое колесо, накапливать электроэнергию, сжать пружину.

 

True or False?

1) An electric circuit is the path taken by an electric current from its source, through the conductors and back to its starting point.

2) The essential parts of any electric circuit are the source of power and the conductors used to transmit the electric current.

3) There are three ways in which electrical appliances! may be connected: (1) simple circuit, (2) series circuit, (3) parallel circuit.

4) A simple circuit is one in which a single resistance is connected across a power source.

5) A series circuit is one in which two or more resistances are connected in one continuous path so that the current passes in turn from one to another.

6) Series circuits are used wherever a constant voltage power supply system is needed.

7) When a circuit contains both series and parallel circuits, it is a combination circuit.

8) Electric circuits possess certain properties which influence the flow of electricity in the circuit.

9) Inductance is a property of a circuit which opposes the flow of electricity.

10) The inductance of a circuit is of no importance only where the current is changing.

 

5. Answer the questions:

1) What are the essential parts of an electric circuit?

2) What are the four ways of connecting electrical circuit components?

3) What is meant by a series circuit?

4) What is a parallel circuit?

5) Where are parallel circuits used?

6) What applications of a combination circuit do you know?

7) What is called a parallel-series circuit (a series-parallel circuit)?

8) What properties do electric circuits possess?

9 What is resistance?

10) When is resistance manifested?

11) What is inductance?

12) When is the inductance of a circuit important?

13) To what may the inductance be compared?

14) What do we understand by capacitance?

 

6. Translate the following into English:

– Привет. Сегодня на уроке мы проходили цепи с различными соединениями, и мне кажется, что я кое-что не понял.

– Hello! Tell me what you haven’t understood.

– Цепь с последовательным соединением – это такой вид цепи, при котором резисторы соединены таким образом, что ток проходит от одного резистора к другому. Насколько я понял, такую цепь удобно использовать там, где необходим стабилизированный источник напряжения.

– You are not quite right. It’s true that in a series circuit there are two or more resistances that are connected in one continuous path so that the current passes in turn from one to another. However, they are used in radio, television, and other electronic equipment. And it is a parallel circuit that is used wherever a constant voltage power supply system is needed.

– Вот как. Значит, цепь с параллельным соединением, в которой ток может проходить по двум или более путям, хорошо подходит для внутренней проводки дома?

– Right you are! House wiring is a good example of the use of this type of circuit.

– Спасибо большое. Теперь мне более понятно.

– Don’t mention it.

 

7. Make up dialogues asking your fellow-student:

a) what a simple circuit is,

b) how many ways of connection there are in an electric circuit,

c) if the series circuits are used in radio and television,

d) what example of the use of the parallel circuit he knows,

e) if a circuit may contain both series and parallel circuits,

f) what properties an electric circuit possesses,

g) what resistance is,

h) what inductance is,

i) what capacitance is.