Give the russian equivalents for the words and word combinations below conductors insulators

1. Translate
   the text into Russian.

Conductors
are materials having a low resistance so that current easily
passes through them. The lower the resistance of the material, the
more
current can pass through it.

The
most common conductors are metals. Silver and copper are the best of
them. The advantage of copper is that it is much cheaper than silver.
Thus copper is widely used to produce wire conductors. One of the
common functions of wire conductors is to connect a voltage source to
a load resistance. Since copper wire conductors have a very low
re­sistance a minimum voltage drop is produced in them. Thus, all
of the applied voltage can produce current in the load resistance.

It
should be taken into consideration that most materials change the
value of resistance when their temperature changes.

Metals
increase their resistance when the temperature increases while carbon
decreases its resistance when the temperature increases. Thus
metals have a positive temperature coefficient of resistance while
carbon
has a negative temperature coefficient. The smaller is the
tem­perature
coefficient or the less the change of resistance with the change of
temperature, the more perfect is the resistance material.

Materials
having a very high resistance are called insulators. Cur­rent
passes through insulators with great difficulty.

The
most common insulators are air, paper, rubber, plastics.

Any
insulator can conduct current when a high enough voltage is applied
to it. Currents of great value must be applied to insulators in
or­der to make them conduct. The higher the resistance of an
insulator, the greater
the applied voltage must be.

When
an insulator is connected to a voltage source, it stores electric
charge
and a potential is produced on the insulator. Thus, insulators have
the two main functions:

to
isolate conducting wires and thus to prevent a short between them and

to
store electric charge when a voltage source is applied.

1. Find answers to these questions in the text above:

1.
What materials are called conductors?

2.
What is the advantage of copper compared with silver?

3.
What is the most common function of wire conductors?

4.
Why is a minimum voltage drop produced in copper conductors?

5.
What is the relation between the value of resistance and the
temperature in
carbon?

6.
What materials are called insulators?

7.
What are the most common insulators?

8.
What are the two main functions of insulators?

2. Complete the sentences using the correct variant:

1.
Insulators
are materials having
a)
low resistance.

b)
high resistance.

2.
Current
passes through conductors a) easily.

b)
with great difficulty.

3.
Copper
and silver are
a)
common conductors.

b)
common insulators.

4.
Air,
paper and plastics are
a)
common insulators.

b)
common conductors.

5.
In case a high voltage is applied to. a) it does not
conduct current

an
insulator
b)
it conducts current.

6.
Insulators are used
a)
to store electric charge.

b)
to
reduce voltage.

c)
to prevent a short between conducting

wires

8.
Carbon decreases its resistance a) when
the temperature in­creases.

b)
when the temperature de­creases.

9.
Metals have a) a positive
temperature coefficient of

resistance

b)
a negative temperature coef­ficient
of

resistance

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Ответ:

1. Give the Russian equivalents of the following words and word combinations:

the course of studies — курс обучения;

primary school — начальная школа;

secondary school — средняя школа;

previously — ранее;

creche — ясли;

lyceum — лицей;

gymnasium — гимназия;

free of charge — бесплатно;

curriculum — программа обучения;

demand — спрос, востребованность;

to adapt — адапировать(ся);

to extend — продлевать;

to conduct — проводить;

transition — переход;

vocational school — профессионально-техническое училище;

higher school — высшая школа;

competitive — конкурентоспособный;

ability — способность;

to be involved in — участвовать в;

postgraduate courses — курсы повышения квалификации/послевузовское образование

2. Find in the text the sentences with the following related words and translate them:

conducting – conductor – conductivity – conductance

3. State questions to the underlined words:

Solid metals conduct electricity with ease.

Conductance depends on the four factors.

There are many kinds of insulation used to cover the wires.

Insulators keep electricity from leaking off the conductor.

Conductors play an important role in electrical engineering.

4. Say whether these sentences are true or false:

Electrical conductivity of a body depends upon its atomic constitution.

There is no difference in the conducting ability of various substances.

The longer the wire is the weaker its opposition is.

The kind of the insulating material depends upon the purpose it is meant for.

Conductors are substances through which electricity is easily transmitted.

Insulators do not allow the electric current to flow freely.

CAPACITORS

A capacitor is one of the main devices widely used in electrical engineering. It is used to store electric charges. Its main parts are metal plates and insulators. y S-
The insulators isolate the plates which store electric the plates. The insulators isolate the plates which store electric charges.

Capacitors are rated in farads (F). In practice units smaller than a farad are commonly used — the microfarad (mF) and the picofarad (pF).

In Fig. 2 one can see two common types of capacitors: a fixed capacitor (a) and a variable one (b). The plates of a fixed capacitor do not move. Thus its capacity does not change.

The plates of a variable capacitor can be moved and its capacity changes.

The value of capacitance depends on the size of the plates and the properties of the dielectrics. It also depends on the distance between the plates: the greater the distance the less is the capacity of a capacitor.

Capacitors are produced in different sizes: from ones with extremely low capacities (1 pF) up to capacitors of extremely high capacity (1000 mF). Fixed capacitors have insulators produced of paper, ceramics and other materials. Variable capacitors have air insulators. Paper capacitors are commonly used in radio and electronics.

1. Choose the correct variant:

1. A capacitor is used a) to produce electric charges. b) to store electric charges.

2. The main parts of a capacitor are a) insulators. b) metal plates and insulators.

3. Capacitors are rated a) in farads, b) in volts, c) in microfarads.

4. The plates of a variable capacitor a) cannot be moved. b) can be moved.

5. The value of a capacitor depends on a) the size of the metal plates. b) the distance between the plates. c) the properties of the insulator.

6. Capacitors are produced a) in a few sizes. b) in many sizes.

2. Complete the sentences:

1. The plates of a fixed capacitor do not move while … . 2. The capacity of a variable capacitor varies while … . 3. The less the distance between the plates the greater the capacity … .

3. Translate the article in writing. Mind “It is … that”. Use a dictionary:

The Capacity of a Capacitor

The capacity of a capacitor is measured in farads. A capacitor has one farad capacity when a charge of one coulomb increases its potential by one volt. The farad is a very large unit. That is why it is the micro­farad that is used to measure the value of capacity.

The microfarad equals one millionth of a farad. If a farad of charge is applied to the capacitor its capacity goes higher by one farad. If charges of equal values are applied to conductors of different sizes, the smaller the conductor the higher becomes its voltage.

RESISTORS. RHEOSTATS. HEATERS

A resistor is one of the most common devices used in electric circuits. Resistors are used to change the value of current and thus to change the value of voltage.

Resistors are produced in different sizes and divided into fixed and variable ones. Fixed resistors have a constant value while the value of variable resistors can be varied. When current flows through resistors their temperature increases; the higher the value of current the greater is the increase in the temperature of a resistor. Any resistor has a maximum temperature to which it may be heated. If this temperature is increased the resistor gets open and opens the circuit.

A device used in the circuit in order to regulate its current is called a rheostat. A rheostat is a wire-wound device; wires for rheostats are produced of materials having high resistivity. Commonly a comparatively short length of wire is used; it is wound on a ceramic or on some other insulator.’ «A slider moving across the windings of the rheostat changes the value of resistance between its terminals.

Another wire-wound device is a heater. Heaters, electric motors, and incandescent lamps are common loads. They are connected into the circuit in parallel since they operate at a constant voltage.

1. Translate the following words:

increase, rheostat, length, slider, winding, terminal; short, incandescent; to increase, to regulate, to call, to wind (wound, wound)

2. Translate the following word-combinations:

rheostat slider, rheostat terminals, load resistance, incandescent lamps, great increase, short lengths, long wire, circuit load; heating element, heated parts, heatable unit, reduced load, reducing value, reduceable resistance

3. Translate the following word-combinations in writing:

current-heated unit, wire-wound devices, current-carrying parts; constantly regulated voltage value, comparatively long steel wire

4. Fill in the verbs «to increase», «to regulate», «to operate», «to call»:

1. What devices are used … the value of power in the circuit? 2. Devices regulating the value of current are … rheostats. 3. When the resistor is heated its temperature … . 4. Motors should … at a constant voltage.

5. Translate the sentences. Mind «since»:

1. Porcelain is widely used as insulating material since its mechanical strength is rather high. 2. Since the tem­perature of the resistor had greatly increased it got open.

6. Choose the correct variant:

A resistor is used a) to reduce the value of current, b) to store electric charges.

The value of a fixed resistor is a) variable, b) fixed.

Devices used to regulate the value of current are called a) capacitors, b) rheostats.

In a wire-wound device the wire has a) low resistance, b) high resistance.

5. Different loads operate a) at a constant voltage, b) at a variable voltage.

6. The value of resistance between the terminals of a rheostat a) varies, b) does not vary.

ELECTRIC LINES AND THEIR EFFICIENCY

Wires are used to deliver electric power and to interconnect different components of electrical installations. Conductors used for electric wiring are commonly pro­duced of copper and aluminium. Aluminium is widely used nowadays due to its low cost. Copper is also widely used in electrical engineering but its cost is much higher.

Cross-sections of copper conductors used nowadays are from 0.5 up to 800 sq mm. Aluminium conductors have the same cross-sections but the minimum one is 2-5 sq. mm.

Wires connecting the components of various, installa­tions may be insulated. They may also be used without insulation. Since in short lengths of wire power loss is exceedingly low one can ignore it. In long wires (longer than 10 m), power loss cannot be ignored since it is rather high. Power loss in a line should not exceed a certain value. If this value is exceeded the line becomes inefficient.

One should know that the efficiency of a line is not constant-it may change. The value of the line efficiency depends on the load: the greater the load the lower is the line efficiency. At voltage losses of 2 to 5 per cent the efficiency of a line is 98-95 per cent. Protecting devices, fuses and relays, are used to protect the circuit against overcurrents and short-circuits.

1. Translate the following words:

installation, cost, cross-section, loss, line, efficiency, per cent; certain, efficient; to ignore, to exceed; nowadays

2. Translate the words and distribute them into four columns (what? what kind? what to do? how?). Mind the suffixes:

efficiency, efficiently, to install, installation, ignorance, to ignore, ignorant, length, wide, width, widely, equal, to equal, equally, equality, to exceed, exceedingly, exceeding

3. Translate the words. Mind the prefixes:

connection-interconnection; to act-to interact; efficient-inefficient; dependent-independent; current-over-current, load-overload

4. Translate the word-combinations in writing:

inconvertible units, interdependent cross-sections, inefficient loss, interchangeable loads, overcharged cells, overheated motor, exceedingly low power losses, constantly changing power efficiency, commonly produced porcelain fuses

5. Fill in the verbs «to exceed», «to interconnect», «to ignore»:

1. Power loss in the line is extremely high; it … a certain value. 2. Various parts of this installation should be … . 3. Power loss in the line is so low that one can … it.

6. Choose the correct variant:

1. Aluminium is used due to its a) high cost. b) low cost and high efficiency.

Cross-section of different conductors a) varies. b) is the same.

Power loss can be ignored a) in short wires. b) in long wires.

A certain value of loss a) can be exceeded. b) should not be exceeded.

Electric lines nowadays are a) efficient. b) inefficient.

Installations are protected a) by switches. b) by fuses.

7. Translate the article in writing:

How to Reduce Heating Losses

When electric energy is produced at the power station, it is to be transmitted over electric wires to the consumer. Wire conductors are known to offer resistance to the current flow; the longer the wire the greater is its resistance to the current flow. Accordingly, the higher the offered resistance the greater are the heating losses in the wire.

One can reduce these undesirable losses in two ways-by reducing either the resistance or the current. To reduce the resistance, it is necessary to make use of a better conducting material and thick wires. But such wires can have a very high cost and, thus, they are considered to be inefficient.

And how can the current be reduced? One of the possible ways to do it is to utilize transformers in the transmission line.

FUSES

Fuses are widely used nowadays as protection devices. They are utilized in various circuits, electrical equipment and installations. Fuses serve to protect them against overcurrents and short-circuits.

There are different types of fuses in use nowadays. Of them, quartz-sand fuses serve for voltages up to 500 volts; fuses of this kind are produced with current ratings of 15 to 60 amp and of 100 to 350 amp.

Fuses are commonly used in low-voltage industrial installations rated up-to 1,000 V.

Fuse protection is based on a very simple principle; in case of a short-circuit or overcurrent, when the max­imum value of current has been exceeded, the fusible link of a fuse is heated to its melting point. This opens the circuit and disconnects the circuit from the power source. In case of a fault, one should replace the faulty fusible element by a new one.

Fuses are used both in direct current (d.c.) and alternating current (a.c.) circuits.

1. Translate the following words:

equipment, quartz, sand, rating, case, link, fault; simple, faulty, direct, alternating; to serve, to base, to place

2. Fill in the verbs «to serve», «to reequip», «to replace»:

1. The lab should be … with modern equipment.

2. This fuse cannot … as a protective element since it is faulty. It should be … with a new fuse.

3. Translate the sentences. Mind «both … and», «in case», «up to»:

1. Both solid and gaseous insulators are in use nowadays. 2. In case an element gets open it should be replaced by a new one. 3. Capacitors of extremely high capacity (up to 1000 mF) are produced nowadays.

4. Choose the correct variant:

A fuse serves a) as a load, b) as a protection device.

Fuses are used a) for d.c. only, b) for both a.c. and d.c .

In case of a fault a) the whole fuse should be replaced, b) the faulty link should be replaced.

Fuse protection is based on, a) a simple principle, b) a complex principle

5. Translate the article in writing. Use a dictionary:

Types of Fuses in Use Nowadays

Fuses are used to protect circuits against overcurrents. In case of an overcurrent, the fuse link made of copper, zink or lead melts and opens the circuit. Zink, lead and their alloys are known to melt at a rather low temperature (200° to 240°C). These metals having a low conductivity, fuse links made from them must have a large cross-sectional area. Copper fuse links have a good conductivity, but they melt at a rather high temperature. As to silver fuse links, they are rather expensive and are known to be used at voltages over 1,000 V and low currents. Most commonly, use is made of copper fuse links silvered for protection against oxidation.

There are several types of fuses in use nowadays. Of them, a plug-type fuse has a porcelain container. Fuses of this type are used for voltages up to 380 V and currents up to 60 amp.

As to a sand fuse, it is used for voltages up to 500 V at currents from 100 to 600 amp.

6. It is interesting to know…

that the efficiency of a heat-power plant is less than half that of a water-power plant.

DIRECT CURRENT AND ALTERNATING CURRENT

We know that current is the flow of electricity through a circuit. Let us consider two main types of current: direct and alternating. A direct current flows through a conducting circuit in one direction only. It flows provided a direct voltage source is applied to the circuit.

An alternating current is a current that changes its direction of flow through a circuit. It flows provided an alternating voltage source is applied to the circuit. Alternating current flows in cycles. The number of cycles per second is termed the frequency of current. In a 60-cycle alternating current circuit the current flows in one direction 60 times per second and in the other direction 60 times per second.

Two frequencies are in use nowadays: the standard for Europe is 50 cycles per second while the standard for the USA is 60 cycles per second. A standard frequency has a great advantage since different electrical systems can be interconnected.

1. Choose the correct variant:

1. Direct current a) changes its direction of flow. b) flows in one direction.

2. Alternating current flows provided a) a direct voltage source is applied. b) an alternating voltage source is applied.

3. The frequency of the current is a) the number of cycles per minute. b) the number of cycles per second.

4. A standard frequency has a) great advantages. b) disadvantages.

5. Different systems can be interconnected a) due to various frequencies. b) due to the standard frequency.

2. Translate the extract in writing. Use a dictionary:

Current densities have greatly increased in the last two decades, due to the invention of new and better insulating materials. Besides, the methods of cooling has also changed.

Ohmic losses disappear when the windings are super cooled. Thus one can use practically any current density in the line. This technology is undergoing a test.

MEASURING DEVICES. AMMETER

According to the electrical quantity being measured, measuring devices are classed into ammeters, voltmeters, wattmeters, etc. Let us first consider the ammeter.

The ammeter serves to measure the value of current in the circuit. When the ammeter is used the circuit should be opened at one point and the terminals of the meter should be connected to it. The ammeter is con­nected to the circuit in series. One should take into consideration that in the process of measuring the pos­itive terminal of the meter is connected to the positive terminal of the source.

The main part of the ammeter is its movement (зд. движущаяся часть). It has the fixed coil and a movable iron core. When the meter is used indications on the scale show the value being measured.

Ammeters are manufactured in different types. Each type serves for a certain range of measurement. In case the quantity being measured exceeds this range, faulty indications result. In such cases the measuring range of the device can be extended by a shunt or by a current transformer.

Moving-coil Ammeter. This meter is used provided the measured quantities are small. Overloading results in faulty indications. Among moving-coil ammeters are galvanometers, microammeters, and milliammeters. In them the movement is connected in parallel with the shunt. Meters of this type are widely used nowadays for engineering measurements. Their advantages are their low cost and their simple construction.

1. Translate the following words:

quantity, consideration, measurement, coil, core, indication, scale, range, shunt; to measure, to take into consideration, to extend, to result (in, from)

2. Fill in the verbs «to exceed», «to result in», «to result from», «to indicate», «to extend»:

1. The range of the meter is small; let us use a shunt to … it. 2. Overloading … faulty indications. 3. A fault in the device may … its constant use. 4. Overcurrent … faulty measurements. 5. Measured quantities should not … a certain range; in case they … this range the meter gives faulty indications.

3. Translate the following sentences:

Let us measure the current in the circuit. Take into consideration the range of the meter. Read the indications off the scale.

4. Choose the correct variant:

1. The ammeter is used to measure a) the value of current. b) the value of power.

2. The main part of the meter is a) its scale. b) its coil. c) its movement.

3. Faulty indications result from a) short-circuits. b) overcurrents.

4. Overcurrents result in a) power loss. b) faulty indications.

5. A shunt is used in order to a) extend the range. b) indicate the range.

VOLTMETER

Voltmeter is used to measure the value of voltage in the circuit. When the voltmeter is being used its positive and negative terminals are connected to the circuit in parallel.

The voltmeter movement is similar in its construction to the ammeter movement: it includes a coil and a high resistor. The scale is calibrated in volts.

In a.c. circuits, in addition to series resistors, the range of measurement is extended by an instrument voltage transformer.

In d.c. circuits, moving-coil meters are commonly used. Their accuracy does not depend either on the value of the external of a voltmeter in magnetic fields or on the temperature.

It depends only on the load. Overloading of the meter results in faulty indications. In order to extend the range of measurements either moving-coil or moving-iron devices are applied.

Moving-iron devices are used in a.c. circuits at power (commercial) frequency. They are produced in accuracy classes 0.1-2.5. Their advantages are a low cost, simplic­ity of construction and reliability of operation.

1. Translate the following words:

accuracy, field; similar, external, reliable; to calibrate, to rely on (upon)

2. Translate the words and distribute them into three columns (what? what kind of? what to do?). Mind the suffixes:

to rely on, reliability, reliable, unreliable, simple, simplicity, accurate, accuracy, similarity, similar, external, inaccurate, dissimilarity, advantageous, disadvantage

3. Translate the word-combinations in writing:

reliable simplicity, unreliable inaccuracy, internal similarity, disadvantageous position, externally interconnected installations, similarly constructed cells, low accuracy class meters, magnetic field range, instrument voltage transformer

4. Translate the sentences. Mind «either … or»:

1. Measuring devices should be connected to the circuits either in series or in parallel. 2. The measuring range of the meter can be extended either by a shunt or by a current transformer.

5. Choose the correct variant:

1. The voltmeter movement a) is similar to the ammeter movement. b) is different from the ammeter movement.

The accuracy of the meter depends on a) the external magnetic field. b) the load.

Low cost and reliability are a) advantages. b) disadvantages.

6. Complete the sentences:

1. The ammeter is used to measure the value of current while … . 2. The ohmmeter is connected to the circuit in parallel while … . 3. High cost and unreliabil­ity are disadvantages while … .

7. Answer the questions:

1. What part of the voltmeter is similar to that of the ammeter? 2. What does the accuracy of a moving-coil meter depend on? 3. What does overloading in the circuit result in? 4. What are the advantages of mov­ing-coil devices?

8. Translate the text in writing:

Electrodynamic Voltmeter

This type of meter includes an electrodynamic movement. Its coils are connected to a series resistor, which serves to extend the range of the instrument and to minimize the effect of temperature variations.

The voltmeter is used both in a.c. and d.c. circuits ; its accuracy class is from 0.1 to 0.5.

OHMMETER

Ohmmeters are widely used nowadays for measuring the value of resistance. The main part of the meter, as in any other direct-indicating device, is its movement. In the ohmmeter’s movement either an external or an internal permanent magnet is used.

The operation of the device either depends on the supply voltage or does not depend on it. Accordingly, the meters are classed into two groups. 1. Meters having a moving-coil movement with two coils on a common shaft. The currents in these coils flow in the opposite directions and, accordingly, two torques are produced. These torques also act in the opposite directions. In the meters of this type a generator serves as a supply source. 2. Devices having a moving-coil movement with a series resistor. In them a battery serves as a supply source.

1. Fill in the verbs «to supply», «to serve as», «to consider», «to act»:

1. Measuring devices are … in units 13-16. 2. Voltage sources … circuits with electric power. 3. The shaft … a base for the coils. 4. The torques produced … in the opposite directions.

2. Translate the sentences. Mind «accordingly»:

1. Meters are used to measure the values of current, voltage, resistance, etc. Accordingly, they are classed into ammeters, voltmeters, ohmmeters, etc. 2. The ohmmeter includes a moving-coil movement with a series resistor; accordingly, in it a battery is used as a supply source.

3. Choose the correct variant:

The ohmmeter serves to measure a) power. b) resistance.

Its movement a) does not include a permanent magnet. b) includes a permanent magnet.

A moving-coil movement has a) coils on two different shafts. b) coils on one common shaft.

In the coils a) two torques are produced. a) one torque is produced.

The currents in the coils flow a) in one direction. b) in two opposite directions.

4. Answer the questions:

1. What does the ohmmeter serve for? 2. What type of magnet does its movement include? 3. How many shafts has the meter? 4. How many torques are produced in the coils? 5. In what directions does the current in the coils flow?

5. Translate the text in writing. Use a dictionary:

Three-Unit Wattmeter

The active power in a four-wire three-phase network is measured by three wattmeters.

These devices are con­nected as shown in Fig. 6, each wattmeter measuring the power in one phase.

It is advantageous to use a three-unit wattmeter since it includes three fixed coils and three movable coils driving a common shaft. The power in a three-phase network can, in this case, be read directly off the device scale.

The power of a symmetrical three-phase -network is found by measuring the power in one phase and multiplying it by three.

6. Render the text in Russian:

Lamps for Music-Making

Lamps for music-making? Certainly. There is a group of gas-dis­charge lamps, called neon glow lamps, whose lights are used as components in electrical circuits. In electronic organs, for example, glow lamps are used as switches that produce light when energized by a key. The light is then modulated to the proper frequency. This «note» is then converted into an electrical signal which is am­plified; so in effect the lamp is producing light that we hear rather than see.

MEASUREMENT OF INSULATION RESISTANCE

According to the code for operation of electrical installations, the minimum insulation resistance is 0.5 meg­ohm. The insulation resistance of lighting and power circuits is measured with a megohmeter. When it is done all the fuses should be removed and the circuit breakers or relays deenergized. The resistance is measured between fuses, or any other protective devices, between any wire and earth and also between any two wires. In the process of measurement one terminal of the megohmeter is connected to the wire and the other terminal to the earthing system. The indications are read off the scale.

The insulation resistance of electrical installations should be checked regularly. If a fault is detected, the faulty part should be eliminated and replaced by a new element.

A fault in the protective part is dangerous for the attending personnel since it may result in an electric shock. For protection against shocks a safety earthing system is used.

1. Choose the correct variant:

The insulation resistance should be checked a) regularly. b) sometimes.

The circuit breakers should be a) energized. b) de-energized.

One terminal should be connected a) to the fuse. b) to the wire.

The other terminal should be connected a) to the protective device. b) to the earthing system.

The faulty part should be a) energized. b) removed.

2. Answer the questions. Use them in a talk with your groupmate:

1. What device is used to measure the insulation resistance? 2. How often should the insulation resistance , be checked? 3. Why should the circuit breaker be deenergized? 4. To what parts should the terminals be con­nected? 5. What should be done with faulty parts? 6. Why is faulty resistance dangerous for attending per­sonnel?

3. It is interesting to know that…

a man can get an electric shock when he comes into contact with the electric fish. One of this kind is found in the tropical waters of South America: it is the electric eel. Small electric eels, one inch long, give a small shock. When the fish is 6 inches long its internal battery gives as much as 200 volts. A very big fish can generate 600 volts! When it is short-circuited, a current of one ampere can be obtained. A two-meter long eel can light a dozen 50 watt lamps. The eel’s head is positively charged and the opposite end is negatively charged.

4. Read the following statements; say whether they are true or false and compare your answers with those given below:

An ammeter is used properly when its terminals are connected to the battery supply. Is it true or false?

One should use an ammeter’s lowest current range during reading indications in order to keep the meter’s internal resistance to a minimum. Is it true or false?

Cleaning a meter face with dry cloth may reduce reading accuracy. Is it true or false?

5. Translate the words and word-combinations:

unreliability, interchange, externally, decentralize; oil-supplied installation, indirectly proportional value, external and internal magnetic fields

6. Use English words instead of the Russian ones:

1. One should (проверять) electric equipment regularly.

2. Electric shock is (опасен) for attending personnel.

3. Faulty elements should be (устранены).

CIRCUIT-OPENING DEVICES. SWITCHES

Any circuit can be divided into an internal and an external part. The internal part consists of the energy source while the external includes the load and the wires.

In addition to these three components, electric circuit utilizes various circuit-opening devices. These devices are classed into non-automatic and automatic. To non-automatic or manually operated devices, belong, switches and controllers. There are different types of switches: knife-switches, packet-switches and others.

The knife-switches are used to start electrical machines. D.c. and a.c . electric circuits are opened and closed by means of knife-switches under normal conditions; they are disconnected by knife-switches under abnormal conditions at no load.

As to packet-switches, they are used to switch on and off electric motors and to close or open electric circuits rated up to 380 V.

Controllers are used in special starting conditions. A controller brings resistors in and out of circuits in order to start, stop or reverse motors. It closes and opens different circuits at different times.

After a switch or a controller is installed it should be given a test. It should be also checked for faultless operation. The device is checked in the on-position and in the off-position. In case the device being checked produces noise or fails to operate, it should be rechecked. The faulty part should be detected and eliminated.

1. Choose the correct variant:

A switch serves a) to start motors, b) to open and close circuits.

The resistance of the switch in the on-position a) is extremely high, b) is rather low.

The external circuit consists of a) the energy source and the wires, b) the load and the wires.

Knife-switches belong to a) manual devices, b) auto­matic devices.

Motors are started, stopped and reversed a) by means of controllers, b) by means of switches.

Electrical devices should be checked a) in the on-position, b) in the off-position.

2. Complete the sentences:

1. The internal circuit includes the energy source: as to … . 2. Switches belong to non-automatic devices; as to … . 3. The knife-switches can operate under abnormal conditions; as to … .

3. Answer the questions:

1. What does а switch serve for? 2. What is the resistance of the switch in the on- and in the off-position? 3. What elements does the external (internal) circuit consist of? 4. What devices belong to manually operated ones? 5. What do controllers serve for? 6. In what position should the devices be checked for faultless operation?

4. Render the extract in English. Demonstrate the operation of а switch while rendering:

Switches are commonly used to open and close circuits. Closed is the on-position; open is the off-position. The switch is in series with the voltage source and its load. In the on-position the closed switch has а very low resistance, which results in maximum current in the load with zero voltage loss across the switch. When the switch is off it has very high resistance and no current flows in the circuit.

5. Translate the text in writing. Use а dictionary:

Disconnecting switches

Application. Indoor disconnecting switches are devices that are intended to make and break electric circuits rated at 6 to 10 kV, a.c. with no load currents. The single-pole disconnecting switches are controlled manually, by means of an insulated rod. The triple-pole disconnecting switches are controlled by means of manual lever-type operating mechanisms.

Mounting Instructions. 1. Clean the switch from dust and dirt. 2. Inspect it on the outside. 3. When insulating the switch, see that the bolts and switch terminals are reliably protected.

6. Translate the article. Describe Fig. 10:

Contactors Туре 370

These contactors consist of the following main parts:

— one fixed bar;

— one magnetic circuit which may be either a.c. оr d.c.;

— one or more auxiliarly contacts (the maximum number of auxiliary contacts is 4);

— one or more poles for use with a.c. or d.c. loads.

These components are to be installed.

Their functions are as follows: fixed bar has the function of supporting all the stationary parts of the contactor. At both ends it is provided with holes for mounting the contactor. Moving shaft is made of steel. It is insulated for the installation of both main pole and auxiliary moving contacts.

RELAYS

Relays are electromagnetic devices widely used in various branches of industry. Relays are designed for rather low currents and for operation in control circuits at low voltages.

Ву means of а relay electric current flowing in one circuit can open or close а second circuit and thus control the switching on and off of а circuit.

The main components of а relay are an electromagnet, an armature and а spring. As to contacts, they belong to its auxiliary elements. When а current starts flowing in the electromagnetic winding, the armature moves and the spring closes the contacts. When there is no current in the primary circuit, the spring pulls the armature and the contacts open.

Fig. 11 shows how а relay is used to control the work of an electric motor. The relay is placed close to the motor which is connected to its secondary circuit. The armature closes the contacts of the secondary circuit, and the motor starts operating. It stops when the relay opens.

The primary circuit is operated either manually or automatically. Every evening and morning street lights are switched on and off from the main panel by means of relays.

As to thermal relays, they use а bimetallic thermal elements. This element consists of two metals differing in thermal coefficients. When the element is heated it actuates the device. It can be heated either directly by the current flowing in it or indirectly by а heater.

1. Translate the sentences. Mind «no»:

1. No heating element can actuate this device. 2. No auxiliary springs were utilized to pull the armature. 3. The switches are faultless; they produce no noise in operation. 4. The operators used no additional springs since no additional components were needed to actuate the relay.

2. Choose the correct variant:

1. Relays are designed for а) low currents. b) high currents.

2. А relay consists of а) а spring and an armature. b) an electromagnet, an armature and а spring.

3. The relay is placed а) close to the motor. b) far from the motor.

4. The motor is connected to а) the primary circuit. b) the secondary circuit.

5. Street lights are switched on and off а) by means of relays. b) by means of controllers.

6. The bimetallic element is heated а) directly. b) indirectly. с) both directly and indirectly.

3. Answer the questions:

1. For what value of current are relays designed? 2. What main parts does а relay consist of? 3. То which circuit is the motor connected? 4. By what means are street lights switched on and off? 5. How is the bimetallic thermal element heated?

4. Translate the text in writing. Use а dictionary:

Magnetic Thermal Relay

Application. This relay is designed for the overload protection of motors connected to а single-phase or to а three-phase a.c. supply. The thermal unit matches the motor temperature and protects it against overloads.

Construction. The relay consists of two main parts: the magnetic unit and the contact box. The magnetic unit includes two coils on а horizontal shaft. А primary coil – for the current to be controlled and а secondary coil connected to а bimetallic bar. The parts of the relay are installed close to each other on а base of insulating material.

Operation. The current to be controlled flows through the primary coil and produces both а magnetic field and а current in the secondary coil. This current flows through the bimetallic bar and heats it. When the current increases above the maximum value, the bar warps. The contaet on the shaft is opened.

TRANSFORMER

А transformer is used to transfer energy; due to the transformer electric energy may be transferred at а high voltage and reduced at the point where it must be used to any value. Besides, а transformer is used to change the voltage and current value in а circuit.

А two-winding device consists of а closed core and two windings (coils). The primary winding is connected to the voltage source; it receives energy. The secondary winding is connected to the load resistance; it supplies energy to the load.

The value of voltage in the secondary winding depends on the number of turns in it. In case the secondary winding has more turns than the primary, the output voltage is greater than the input voltage. А device of this type steps up the voltage and is termed а step up transformer (see Fig. 12). In case the secondary winding has fewer turns than the primary, the output voltage is lower than the input. This device decreases or steps down the voltage. It is termed а step down transformer.

Let us compare Т1 and Т2. Т2 has an iron core: it is used for low frequency currents. T1 has an air core and is used for high frequencies.

The core and the windings are placed in а metal tank. The tank contains the insulating oil, which protects the device from overheating and cools its parts. The higher is the capacity of the device the greater is the cooling required.

Each transformer has а nameplate attached to the tank. It bears the transformer’s ratings, its type, its capa­city, number of phases, group of winding, frequency, duty ratings, method of cooling, indoor or outdoor, mass, the name of the plant and some other data.

When the new transformer is installed its tank is earthed. After that the device is given а test to check its operation. During the test one should listen to its noise by means of а bakelite tube, 1 meter long. In the case of the abnormal noise or in the case of oil decrease in the tank, the device should be switched off and examined.

Common faults in а transformer are an open in the winding, а short between the primary and the secondary, and а short between turns. Shorted turns are due to periodic overloads or dynamic stress. An open may result from overheating. Stresses result from short circuit currents.

In case а transformer has а fault, it stops operating or its operation is poor. А faulty element should be eliminated and replaced by а new one.

The transformer forms one of the main parts of а substation.

1. Translate the following words:

winding, turn, input, output, tank, nameplate; poor; to transfer, to receive, to step up, to step down, to contain, to cool, to require, to attach

2. Translate the word-combinations in writing:

а) input voltage, voltage output, step up transformer, step down transformer, regular operation, poor results

b) modern network protection relay, high-voltage current transformer, faultlessly operating step up transformer, poorly operating step down transformer, external hard porcelain insulator

3. Fill in the verbs «to attach», «to contain», «to receive», «to supply», «to require»:

1. Any operating transformer … cooling; thus its tank … cooling liquid. 2. The new apparatus is to be … to the panel; this attachment is not simple. It … experience. 3. The Т windings … and … electric energy. 4. Any device … testing.

4. Choose the correct variant:

1. А transformer is used а) to reduce power. b) to receive power. с) to transfer power.

2. The primary winding а) receives energy. b) supplies energy.

3. А step down transformer а) increases the voltage. b) decreases the voltage.

4. А transformer with an iron core is used а) for low frequency currents. b) for high frequency currents.

5. The nameplate is attached а) to the frame. b) to the tank.

6. The tank contains а) air. b) oil.

7. Faults in а transformer result from а) overheating. b) stresses. с) short-circuits.

5. Complete the sentences:

1. The primary winding receives energy while … . 2. А step down transformer decreases the voltage while … . 3. А transformer with an air core is used for high frequencies while … . 4. In a step up transformer the number of turns in the secondary winding is greater that the number of turns in the primary while … . 5. The greater is the quantity of heat the greater is the cooling required while … .

6. Answer the questions:

1. What is а transformer used for? 2. What parts does it consist of? 3. What is the function of the primary (secondary) winding? 4. What is the difference between а step up and а step down Т? 5. What frequencies is an air (iron) core Т used for? 6. Where are the core and the windings placed? 7. What liquid does the tank contain? 8. Why does а Т require cooling? 9. What are the common faults in а Т? 10. What do they result from? 11. То what part is the nameplate attached? 12. What data does it bear?

7. Translate the text in writing. Use а dictionary:

High-Voltage Transformer

А great number of different types of transformers are in use nowadays. А high-voltage transformer is one of the newly constructed ones.

This transformer is intended for outdoor installation. Its highest system voltage is 75.5 to 525 kV; maximum number of cores is 6 and frequency – 50 and 60 Hz.

The transformer is applied in high voltage installations and for energization of network protection relays. The device has unlimited electrodynamic short-circuit strength of the primary conductor. Protection cores are suitable for overcurrent requirements as well as for reliable transformation of short-circuit currents. For external insulation hard porcelain is used and for the main insulation paper / oil insulation is used.

8. Translate the words and the word-combinations:

disappearance, overproduction, uselessness, outdoor, indoor, poorly operating relay, manually-operated switch, unearthed live tank

BATTERIES

An Italian scientist Alessandro Volta made a lot of experiments with electricity. Batteries as sources of electrical energy are the result of his experiments.

Today battery cells are produced in two common forms: dry cells, used in flashlights, portable radios, clocks, cameras and (well) wet cells, used in automobiles, airplanes, boats.

The voltaic cell is composed of three parts: a pair of dissimilar metal plates called electrodes, a dilute acid solution called electrolyte, and a nonconducting container called the cell. In a glass container filled with sulphuric acid there are two plates: one copper and are connected by a copper wire, electricity will flow through it from the copper plate to the zinc plate.

For the voltaic cell the copper plate is the positive electrode and the zinc plate the negative electrode a copper wire will convey electricity and is called an electrical conductor. Copper, aluminium and silver are good conductors. They must be surrounded by protective material which does not conduct electricity. Such materials are called electrical insulators (glass, wood, rubber, some plastics, insulation tape)

Remember that faulty insulation is dangerous and leads to unwanted electrical flow and probably to local overheating.

Vocabulary: