ELECTRICITY
Exercise 1. Memorize the active vocabulary to text 1:
electric charge - електричний заряд
particles - часточка
to take place - проходити, відбуватися
to transmit - передавати
to generate – виробляти
to convert - перетворювати
to take a part – брати участь
sources - джерело
amount -кількість
electric current – електричний струм
Exercise 2. Read, translate and retell text 1.
Text 1. Electricity
Electricity is one of the basic forms of energy. Electricity is associated with electric charge, a property of certain elementary particles such as electrons and protons, two of the basic particles that make up the atoms of all ordinary matter. Electric charges can be stationary, as in static electricity, or moving, as in an electric current.
Electrical activity takes place constantly everywhere in the universe. Electrical forces hold molecules together. The nervous systems of animals work by means of weak electric signals transmitted between neurons (nerve cells). Electricity is generated, transmitted, and converted into heat, light, motion, and other forms of energy through natural processes, as well as by devices built by people.
Electricity can be generated in many ways and from many different sources. It can be sent over long distances. Electricity can also be converted into other forms of energy, and it can be stored. Electricity takes a part in nearly every aspect of modern technology. Electricity provides light, heat, and mechanical power. It makes telephones, computers, televisions, and countless other necessities and luxuries possible.
Exercise 3. Translate word combinations with the term
Electrical power, electrical force, electrical current, electrical device, electrical instruments, electrical battery, electric charge
Exercise 4. Make up sentences with the following terms.
to take place, to transmit, to generate, to convert, to take a part, to contain, to flow
Exercise 5. Complete the following sentences.
1. Electricity is__________. 2 Electric charges can be __________. 3 Electricity is converted into ___________. 4 Electricity can be generated from__________. 5. Electricity provides ______________. 6 Electricity consists of _______________. 7 Electric charge can be ___________. 8 Static electricity consists of_____________. 9 An electric current is_________
Exercise 6. Answer the questions on text 1.
1. What is electricity? 2. What is electric charge? 3. What elementary particles can you name? 4. What do electrons and protons make up? 5. What types can be electric charge? 6. Where does electric activity take place? 7. What is electricity generated, transmitted, and converted into? 8. What does electricity provide? 9. What makes the necessities possible?
Exercise 7. Translate into English
1. Електрика – це одна з форм енергії. 2.Такі частини як електрон та протон мають електронний заряд. 3. Електрична активність відбувається у всьому світі. 4. Електрика трансформується в тепло, світло, рух та інші форми енергії. 5. Електрика виробляється багатьма шляхами. 6. Електрика виробляється від різних джерел. 7. Електрика може бути накопичена. 8. Електрика може бути передана на великі відстані. 9. Електрика бере участь майже в кожному аспекті сучасного життя. 10. Електрика забезпечує світло, тепло, механічні машини.
Exercise 8. Memorize the active vocabulary to text 2:
To redistribute – здійснювати перерозподіл
to flow – текти
copper wire – мідний дріт
direct current – постійний струм
alternating current – змінний струм
reverse – зворотній напрям
resistance – опір
meter – вимірювальний прилад
outlet – розетка
voltage – напруга
conductor – провідник
circuit – електричне коло
equation – рівняння
to allow – дозволяти
insulator – діелектрик
Exercise 9. Read and translate text 2:
Text 2. ELECTRIC CURRENT
An electric current is a movement of charge. When two objects with different charges touch and redistribute their charges, an electric current flow s from one object to the other. If two objects are connected by a material that lets charge flow easily, such as a copper wire, then an electric current flows from one object to the other through the wire.
Current that flows in one direction only is called direct current. Current that flows back and forth, reversing direction again and again, is called alternating current. Direct current, which is used in most battery-powered devices, is easier to understand than alternating current. A flow of direct current starts from a battery or generator, passes through resistance s, meter s, motors and so on and finally returns to its starting point. A direct current is used in the electrical system of an automobile and an airplane, in the tram, telegraph, telephone, in industry, etc. Alternating current is used in most devices that are plugged in to electrical outlets in buildings.
Other properties that are used to quantify and compare electric currents are the voltage (also called electromotive force) and the resistance of the conductor to the passage of the current. The amount of current, voltage, and resistance in any circuit are all related through an equation called Ohm’s law.
Conductors are materials that allow an electric current to flow through them easily. Most metals are good conductors. A good conductor is one that has low resistance. Silver is the best conductor and copper is the second best. Electric wires are usually made of copper, which is less expensive than silver.
Substances that do not allow electric current to flow through them are called insulator s, nonconductors. A good insulator has a very high resistance. Rubber, glass, and air are common insulators. Electricians wear rubber gloves so that electric current will not pass from electrical equipment to their bodies.
There are several different devices that can supply the voltage necessary to generate an electric current. The two most common sources are generators and electrolytic cells.
Exercise 10. Answer the following questions:
1. What is electric current? 2.In what conditions does the current flow? 3. What is direct current? 4. What current is alternating current? 5. Where is DC used? 6. What is the way that the current flow? 7. Where current is used in electrical outlets? 8. What properties are used to quantify the current? 9. By means of what equation we can count the amount of current? 10. What is conductor? What materials are good conductors? 11. What are insulators? 12. Why do the electricians wear rubber gloves? 13. What devices can generate an electric current?
Exercise 11. Translate into English:
1. Електричний струм – це рух заряджених частинок. 2. Постійний струм – це струм, що рухається в одному напрямку. 2. Змінний струм – це струм, що змінює напрямок. 3. Потік постійного струму стартує від джерела струму, проходить через опір, лічильники та вертається в початкову точку. 4. Змінний струм використовується для приладів, що включені в розетку. 5. Кількість струму, опору чи напруги можливо обчислити рівнянням закону Ома. 6. Провідники це матеріали, що дозволяють струму легко проходити крізь. 7. Більшість металів провідники. 8. Діелектрики – це матеріали, що не дозволяють струму проходити крізь. 9. Гума, скло та повітря –діелектрики. 10. Генератори та батареї виробляють електричний струм.
Exercise 12. Find the meaning of the terms:
| AC | a device for storing energy that can be converted into electrical power |
| outlet | any material or device with a very low electrical conductivity |
| battery | a point on a wiring system at which current is taken to supply electric devices |
| insulator | an electric current that moves in one direction |
| DC | an electric current that repeatedly changes its direction |
Exercise 13. Complete the text with the missing information
Electrons, air, resistance, flow, conductors, free
Electricity is a ____1___ of free electrons along a conductor. To produce this current flow, a generator is placed at the end of the conductor in order to move the ____2_____
Electricity needs a material which allows a current to pass through easily, which offers little ___3__ to the flow and is full of free electrons. This material is called a conductor and can be in the form of a bar, tube or sheet. The most commonly used ___4__ are wires, they can be in different sizes and thicknesses. They are coated with insulating materials such as plastic.
A material which contain less ___5___ electrons is called an insulator. Glass, rubber, dry wood and ___6___ resist the flow of electric charge, and as such are good insulating materials.
Exercise 14. Find out if the following statements are true or false
1. A flow of electrons moving inside a conductor creates an electric current. 2. A generator is used to move the charges. 3. Electrons can easily pass through any material. 4. Any material is good conductor. 5. Conductors are coated with insulators. 6. The presence of free electrons affects the conductivity of materials. 7. Insulating materials resist the flow of electrons. 8. There are 3 types of electric source. 9. Every metal is conductor. 10. Electricians wear rubber gloves to protect electrical equipment.
Exercise 15. Memorize the active vocabulary to text 3:
a circuit – електричне коло
a flashlight – ліхтарик
a bulb – лампочка
a terminal – клема
a load – навантаження
a switch – перемикач
a circuit breaker – автомат захисту
a fuse – запобіжник
a filament – нить накалювання
to glow – світити
Exercise 16. Read and translate text 3:
Text 3. ELECTRIC CIRCUITS
This illustration shows the electric circuit used in a simple flashlight. Current, provided by a battery, flows through a wire, into a bulb, and through another wire back to the battery. As the current flows through a tiny wire inside the bulb (the filament), it heats and glow s.
All electric circuit is a pathway through which the electric current can flow. A simple circuit consists of a power source, two conducting wires, each one attached to a terminal of the source and a device through which electricity can flow. This device is called a load and it’s attached to the wires. If all the parts are properly connected, the current flows and the bulb lights up.
There can be a switch on one of the connecting wires. A flashlight is an example of such a circuit. When the switch is open, the connection is broken, electric current cannot flow through the circuit, and the bulb does not light. When the switch is closed, current flows and the bulb lights.
The bulb filament may burn out if too much electric current flows through it. To prevent this a fuse or circuit breaker may be placed in the circuit. When too much current flows through the fuse, a wire in the fuse heats up and melts, thereby breaking the circuit and stopping the flow of current.
The part of an electric circuit other than the source of electric current is called the load. The load includes all devises placed in the circuit, such as lights, electro motors, heaters or speakers. It also includes the connecting wires, as well as switches, fuses, and other devices. The load forms a continuous conducting path between the terminals of the current source.
There are two basic ways in which the parts of a circuit are arranged. One arrangement is called a series circuit, and the other is called a parallel circuit.
Exercise 17. Name the elements on the scheme
Exercise 18. Open brackets and use the correct form of verb
1. I (to use) electricity every day. 2. Battery (to generate) direct current. 3.Yesterday it (to generate) big amount of current. 4. I (to use) pocket flashlight last week. 5. He (to use) wire in circle now. 6.Wire (to connect) the battery and bulb. 7.The bulb (to light) now. 8. Fuse (to prevent) electric circuit. 8. The fuse (to melt) yesterday. 9. All circuits (to consist) of electrical source, wires and load. 10. Every flashlight (to consist) of battery, wire and bulb.
Exercise 19. Complete the following sentences.
1. In circuit current flows from _____ to______. 2. Electric circuit is ______. 3. The load is a device, that ______. 4. The switch is used for ______. 5. If the switch is open the current _____. 6. If the switch is closed the current _______. 7. The fuse is used to _______. 8. If too much current flows through the fuse it will ______.
Exercise 20. Match the terms with their definitions
| load | a) a device which interrupts the circuit |
| switch | b) a circuit in which wires are disconnected |
| source | c) a device which provides power |
| fuse | d) a complete circuit with no breaks at all |
| closed circuit | e) a device which consumes electric power |
| broken circuit | f) a protective device |
Exercise 20 Answer the questions on text 3.
1. What does a simple circuit consist of? 2. Where can you find the example of simple circuit?
3. How does the current flow in the circuit? 4. What device can prevent filament from burning? 5. What is switch used for? 6. What appliances can be load? 7. What are the types of circuit arrangement?
Exercise 21. Translate into English:
1. Електричне коло – це шлях яким протикає струм. 2. Струм в колі стартує від джерела електричної енергії, проходить через навантаження та повертається в початкову точку. 3. Провідники прикріпленні до клем джерела електричної енергії. 4. Навантаження – це пристрій, що приєднаний провідниками до джерела електричної енергії. 5. Навантаженням можуть бути лампочки, електромотори, навушники, нагрівачі. 6. Перемикач – це пристрій для з’єднання та роз’єднання електричного ланцюга. 7. Коли перемикач відкрито, то струм не може протікати по колу. 8. Коли перемикач закрито, то коло з’єднане. 9. В електричному ліхтарю струм протікає від батареї по провідникам та нитці накалювання, через це лампочка світиться. 10. Якщо через нить накалювання проходить забагато струму вона може згоріти. 11. Запобіжник використовується для запобігання перегріву навантаження. 12. Запобіжник може розплавитися та роз’єднати коло, коли струму забагато. 13. Існує два типи організації електричних кіл послідовне та паралельне.
Exercise 22. Memorize the active vocabulary to text 4:
coulomb – кулон
to measure - вимірювати
electromotive force – електрорушійна сила (ЕРС)
сollision – зіткнення
to interfere – заважає
cross-sectional area – площа поперечного перерізу
thickness – товщина
Exercise 23. Read and translate text 4:
4 MEASURING ELECTRIC CURRENT
Electric current is measured in units called amperes (amp). If 1 coulomb of charge flows past each point of a wire every second, the wire is carrying a current of 1 amp. If 2 coulombs flow past each point in a second, the current is 2 amp.
Voltage. When the two terminals of a battery are connected by a conductor, an electric current flows through the conductor. One terminal continuously sends electrons into the conductor, while the other continuously receives electrons from it. The current flow is caused by the voltage, or potential difference, between the terminals. The more terminals are giving up and receiving electrons, the higher the voltage. Voltage is measure d in units called volts. Another name for a voltage produced by a source of electric current is electromotive force.
Resistance. A conductor allows an electric current to flow through it, but it does not permit the current to flow with perfect freedom. Collisions between the electrons and the atoms of the conductor interfere with the flow of electrons. This phenomenon is known as resistance. Resistance is measured in units called ohms. The symbol for ohms is the Greek letter omega, Ω.
The resistance of a piece of wire depends on its length, and its cross-sectional area, or thickness. The longer the wire is, the greater its resistance. If one wire is twice as long as a wire of identical diameter and material, the longer wire offers twice as much resistance as the shorter one. A thicker wire, however, has less resistance, because a thick wire offers more room for an electric current to pass through than a thin wire does. Scientists describe this relationship between resistance, length, and area by saying that resistance is proportional to length and inversely proportional to cross-sectional area.
Usually, the higher the temperature of a wire, the greater its resistance. The resistance of some materials drops to zero at very low temperatures. This phenomenon is known as superconductivity.
Ohm’s Law. The relationship between current, voltage, and resistance is given by Ohm’s law. This law states that the amount of current passing through a conductor is directly proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor. Ohm’s law can be expressed as an equation, V = IR, where V is the difference in volts between two locations (called the potential difference), I is the amount of current in amperes that is flowing between these two points, and R is the resistance in ohms of the conductor between the two locations of interest. If any two of the quantities are known, the third can be calculated.
Under normal conditions, resistance is constant in conductors made of metal. If the voltage is raised to 220 in the example above, then R is still 11. The current I will be doubled, however, since I = V/R = 220/11 = 20 amp.
Exercise 24. Make up sentences with the following terms.
To allow, allowance, to flow, a flow, to conduct, a conductor, to resist, a resistance.
Exercise 25. Find the equivalents
| coulomb cause permit ohm omega length relationship law quantities constant | ом дозволяти кількість співвідношення довжина закон постійний причиняти кулон омега |
Exercise 26. Complete the following sentences.
1. Electric current is measured in _____. 2. Аn electric current flows through _____. 3. The potential difference between the terminals is called ____. 4. Voltage is measured in _____. 5.Collisions between the electrons and the atoms of the conductor _____. 6. Resistance is measured in_____. 7. The resistance of a piece of wire depends on ____. 8. The resistance is proportional to length and inversely proportional to _____. 9. The relationship between current, voltage, and resistance is_____. 10. The amount of current passing through a conductor is directly proportional to _____ and inversely proportional to_____.
Exercise 27. Answer the questions on text 4.
1. What unit is the electric current measured? 2. What is voltage? 3. What unit is voltage measured? 4. What is resistance? 5. What unit is resistance measured? 6. What does resistance depend on? 7. What is superconductivity? 8. What is Ohm’s law? 9. What does the Ohm’s law state?
Exercise 28. Memorize the active vocabulary to text 5:
electromagnetic induction - електромагнитна індукція
majority – більшість
to employ
in relationship – у відповідності
alternator – генератор змінного струму
either …or – і-і
to consume
magnet - магнит
polarity – полярність
north and south poles – північний та південний полюси
Exercise 29. Read and translate text 5:
Text 5. ELECTROMAGNETIC GENERATION OF POWER
Electrical energy can be produced through a number of methods. Common methods include the use of light, pressure, heat, chemical and electromagnetic induction. Of this processes, electromagnetic induction is most responsible for the generation of the majority of the electrical power used by humans. Virtually all mechanical devices (generators and alternators) that produce electrical power employ the process of electromagnetic induction. The use of light, pressure, heat, and chemical sources for electrical power is found on aircraft but produce a minimal amount of all the electrical power consumed during a typical flight.
Electromagnetic induction is the process of producing a voltage (EMF) by moving a magnetic field in relationship to a conductor. As shown in figure, when a conductor is moved through a magnetic field, an EMF is produced in conductor. If a complete circuit is connected to the conductor, the voltage also produces a current flow.
It is the relative motion between a conductor and a magnetic field that caused current to flow in conductor. Either the conductor or magnet can be moving or stationary. When a magnet and its field are moved through a coiled conductor, a DC voltage with a specific polarity is produced. The polarity of this voltage depends on the direction in which the magnet is moved and position of the north and south pole of magnetic field.
Exercise 30. Complete the following sentences.
1. Electrical energy can be produced____. 2. Electromagnetic induction is most responsible for___. 3. Alternator produces electrical power employ ____. 4. ____ sources for electrical power is found on aircraft. 5. ____ produce a minimal amount of all the electrical power consumed during a typical flight. 6. Electromagnetic induction is the process of___. 7. When a magnet is moved through a coiled conductor___. 8. The polarity of this voltage depends on___.
Exercise 31. Answer the questions on text 5.
1. How can electrical energy be produced? 2. What are the methods of producing electrical energy? 3. What sources of electricity can be found at the aircraft? 4. What of them are not primary and why? 5. What is EMF? 6. How can current be produced by menace of EMF? 7. Should the magnet be only stationary? 8. What polarity direction depends on?
Exercise 32. Memorize the active vocabulary to text 6:
Advantage – перевага
variety – різноманіття
applications - пристрій
laminated iron core
winding – обмотка
to be mounted - установлений
desired – що потребується
step-up transformer
step-down transformer
number of turns – кількість витків
cycle – цикл
Text 6. TRANSFORMERS
One of the great advantage in the use of the alternating current is ease with which the voltage may be changed by means of a relatively simple device known transformers. Although there are many different types of transformers, and a great variety of different applications, the principles of action are the same in each case.
The basic arrangement consists of a laminated iron core forming a closed magnetic circuit on which two separate windings are mounted. One winding, called primary, is connected to the AC supply, and other winding, the secondary, produces a voltage which can have any desired value.
Transformers provide us with a means of stepping up or down an AV voltage. For step-up transformer the secondary voltage will be greater than the primary. For step-down transformer the secondary voltage will be less than the primary. The amount of voltage is proportional to the number of turns in coil and to the rate at which the magnetic field varies. With a normal AC supply connected to the primary, the field changes at a uniform rate throughout each cycle and a voltage appears in secondary.
Exercise 34. Complete the following sentences.
Exercise 35. Answer the questions on text 5.
Exercise 36. Memorize the active vocabulary to text 7:
rectifier – випрямлювач
one-way conductivity – однобічна провідність
half-wave rectifier – однонапівперіодний випрямлювач
full-wave rectifier – двохнапівперіодний випрямлювач
centre tap – вивід від центральної частини вторинної обмотки трансформатора
is grounded – заземлений
pulsations frequency –частота пульсацій
to filter out –відфільтрувати
electromotive force – електрорушійна сила
to drive –примушувати рухатися
ground –заземлення
rectifying diode –діод, що випрямовує
frame of reference –система координат
to plot –будувати (криву)
functional dependence - функціональна залежність
rectangular –прямокутний
origin – початок системи координат
axes – оси (pl);axis – вісі (множ.)
Exercise 37. Read and translate text 6:
Text 7. RECTIFIER
Rectifier is an electronic device for converting alternating current from the mains into direct current, necessary for computer circuits. All rectifiers operate on the principle of one-way conductivity of a rectifying diode. One-way conductivity means that the rectifying diode conduct current in one direction and does not conduct current in the opposite direction.
All rectifiers consist of three main parts:
(1) Power transformer, which is connected to the mains,
(2)Rectifying diode,
(3)Load.
There are two main types of rectifiers. The first type is called half-wave rectifier, the second type is called full-wave rectifier. In a half-wave rectifier the secondary winding of the power transformer does not have any center tap and the frequency of pulsations at the output is fifty cycles per second. In a full-wave rectifier the secondary winding of the power transformer has a centre tap, which is grounded, and there are two rectifying diodes. The pulsations frequency at a full-wave rectifier is one hundred cycles per second, which is much easier to filter out.
During the first half-cycle of the AC voltage, the electromotive force (EMF), developed in the secondary winding of the power transformer, drives the current from the ground to the rectifying diode. In this direction the diode conducts and the current flows through the load. During the second half-cycle the electromotive force changes for the opposite and drives the current from the diode to the ground. In this direction the diode does not conduct and no current flows through the load.
The frame of reference, used for plotting the functional dependence of current from time is called the rectangular frame of reference. It consists of the origin and two axis- the axis of the variable (horizontal) and the axis of the function (vertical).
Exercise 38. Answer the questions on text 6.
1. What are rectifiers for? Where are they used? 2. What is the principle of their operation? 3. What parts does a rectifier consist of? 4. How do we understand one-way conductivity? 5. What types of rectifiers do we know? 6. How do we call the first type of rectifiers? 7. Why are these rectifiers called half-wave? 8. What is the pulsation frequency at the output of these rectifiers? 9. What are advantages and drawbacks of half-wave rectifiers? 10. How do we call the second type of rectifiers? 11.Why are these rectifiers called full-wave? 12. What parts does a full-wave rectifier consist of? 13. How many diodes does a full-wave rectifier use? 14. What is the pulsations frequency at the output of a full-wave rectifier? 15. What are advantages and drawbacks of full-wave rectifiers? 16. How can we convert pulsating current into direct current? 17. What must we use for visual presentation of functional dependence of rectified current from time? 18. What are the main parts of the rectangular frame of reference? 19. What do we usually plot along the horizontal axis of the rectangular frame of reference?
Exercise 39. Complete the following sentences.
Exercise 40. Memorize the active vocabulary to text 8:
Amplify – посилювати
semiconductor – напівпровідник
the junction triode
ohmic lead
emitter – емітер
collector – колектор
injecting contact
Exercise 41. Read and translate text 8:
Text 8. TRANSISTORS
The transistor is a semiconductor devise for the amplification of electric signals. The transistor of the greatest importance at present is the junction triode. This transistor contains three district regions of semiconductor, each heaving an ohmic lead. A junction transistor can be regarded as composed of two p-n junctions separated by a thin base region. The left hand junction is called the emitter, the right hand side- the collector. The p-n emitter-base junction is forward biased while the p-n collector-base junction is reverse-biased.
The emitter acts as an injecting contact and injects electrons into the base region under the influence of very small emitter signal. There they diffuse until are caught by the collector field. The collector circuit has a much higher impedance and voltage level then those of the emitter circuit. The transfer of charge from the low-impedance emitter to the higher-impedance collector circuit yields power amplification. There are two types of transistors based upon their structure, the n-p-n and the p-n-p. Their modes of action are similar; the roles of electrons and holes are interchanged in these two arrangements.
Exercise 42. Find the equivalents
| An amplifier A gird An emitter Apart The soot Arsenic A bias A fuse Impurities | a) Сажа b) Окремо c) Миш`як d) Запобіжник e) Підсилювач f) Решітка g) Емітер h) Домішки i) Зміщення |
Exercise 43. Translate fallowing word-combinations
Омічний вивід; емітерний перехід прямо зміщений; колекторний перехід зворотно зміщений; підсилювач потужності; доки вони не попадуть у поле колектора; величина напруги; ланцюг колектора з високим опором -
Exercise 44. Complete the following sentences.
1. The transistor is a semiconductor devise for…2. The transistor of the greatest importance at present is the… 3. This transistor contains… 4. Base district regions heaving an… 5. A junction transistor can be regarded as composed of two p-n junctions separated by…6. The left hand junction is called… 7. … has a much higher impedance and voltage level than those of the emitter circuit. 8. There are two types of transistor …
Exercise 45. Answer the questions on text 8.
1. What is transistor? 2. What transistor is of the greatest importance at present? 3. What does this transistor contain? 4. What function does the transistor perform? 5. What advantages of using transistors are? 6. Where is the transistor used? 7. How does the base work? 8.What is the main component of the transistor?
Exercise 46. Translate fallowing word-combinations
Solid; junction; diffused; majority; specimen; conductivity; hole; carriers; charge
Exercise 47. Memorize the active vocabulary to text 9:
Amplifier – посилювач
output power - сила на виході
ratio – відношення
solid state amplifier – посилювач на інтегральних схемах
plate – анод
control grid – керуюча сітка
cathode – катод
collector – колектор
base – база
emitter – емітер
Exercise 48. Read and translate text 9:
Text 9 AMPLIFIER
Amplifier is an electronic device for stepping up power of the signal. All amplifiers operate on the principle of controlling very large amount of output power by very small amounts of input power, applied to the control electrode. Amplification factor of an amplifier is calculated as the ratio of its output power to input power. There are two main types of amplifiers: 1) Vacuum tube amplifiers, and 2) Transistor, or solid state, amplifier.
Vacuum tube amplifier consists of plate, control grid, cathode. Control grid controls current flowing through the tube. Cathode emits electrons. Filament heats the cathode, enabling the process of electronic emission. By their nature vacuum tubes are high voltage devices because voltages are high, but current are low.
Transistor amplifier consists of collector, base and emitter. Base controls current flowing through the transistor. Emitter emits electrons. Collector collects electrons, arriving from emitter. By their nature transistors are current device because currents are high, but voltages are low.
Exercise 49. Answer the questions on text 9
1. What are amplifiers used for? 2. What is the principle of their operation? 3. What does the control electrode of an amplifier do? How is the amplification factor of an amplifier defined? 5. How many types of amplifiers do you know? 6. What are the components of a vacuum tube amplifier? 7. What does the control grid of vacuum tube amplifier do? 8. Why is it necessary to heat the cathode? 9. Why are vacuum tubes called high voltage device? 10. What parts does the transistor amplifier consists of? 11. Why are transistors called current device? 12. What does the base electrode of a transistor amplifier do? 13. What does the collector electrode of a transistor amplifier do? 14. Is there anything in common between the base electrode of a transistor and the control grid vacuum tube?
Exercise 44. Complete the following sentences
1. Amplifier is an electronic device for___. 2. All amplifiers operate on the principle of controlling ___. 3. Amplification factor of an amplifier is calculated as the ___. 4.There are two main types of amplifiers___. 5. Transistor amplifier consists of _____. 6. Base controls current flowing ___.7. Emitter _____. 8. Collector collects ______. 9. By their nature transistors are current device because _________.
Exercise 45. Open brackets and use the correct form of verb
1. I (to use) electricity every day. 2. Battery (to generate) direct current. 3.Yesterday it (to generate) big amount of current. 4. I (to use) pocket flashlight last week. 5. He (to use) wire in circle now. 6.Wire (to connect) the battery and bulb. 7.The bulb (to light) now. 8. Fuse (to prevent) electric circuit. 8. The fuse (to melt) yesterday. 9. All circuits (to consist) of electrical source, wires and load. 10. Every flashlight (to consist) of battery, wire and bulb.
Exercise 46. Match the terms with their definitions
| Transformer | a) an apparatus in which current flows more readily in one direction than the other, for changing an alternating current into a direct current |
| Transistor | b) an electronic device used to increase the strength of the signal fed into it |
| Rectifier | c) an electronic device that controls the flow of an electric current, most often used as an amplifier or switch |
| Amplifier | d) an electric device consisting essentially of two or more windings wound on the same core |
Exercise 47. Translate into English:
1. Електричне коло – це шлях яким протикає струм. 2. Струм в колі стартує від джерела електричної енергії, проходить через навантаження та повертається в початкову точку. 3. Провідники прикріпленні до клем джерела електричної енергії. 4. Навантаження – це пристрій, що приєднаний провідниками до джерела електричної енергії. 5. Навантаженням можуть бути лампочки, електромотори, навушники, нагрівачі. 6. Перемикач – це пристрій для з’єднання та роз’єднання електричного ланцюга. 7. Коли перемикач відкрито, то струм не може протікати по колу. 8. Коли перемикач закрито, то коло з’єднане. 9. В електричному ліхтарю струм протікає від батареї по провідникам та нитці накалювання, через це лампочка світиться. 10. Якщо через нить накалювання проходить забагато струму вона може згоріти. 11. Запобіжник використовується для запобігання перегріву навантаження. 12. Запобіжник може розплавитися та роз’єднати коло, коли струму забагато. 13. Існує два типи організації електричних кіл послідовне та паралельне.
Для підготовки до заліку ви маєте знати:
- наступні терміни англійською мовою:
| електричний заряд джерело кількість електричний струм постійний струм змінний струм опір напруга провідник діелектрик електричне коло напівпровідник емітер колектор посилювач | клема навантаження перемикач автомат захисту запобіжник електрорушійна сила (ЕРС) ом кулон полярність генератор змінного струму пристрій обмотка випрямлювач заземлений вісь | проходити, відбуватися передавати виробляти перетворювати дозволяти вимірювати посилювати текти |
- знати відповіді на питання:
What is electricity?
What elementary particles can you name?
What can electricity be converted into?
What is electric current?
What is direct current? Where is DC used?
What current is alternating current? Where is AC used?
What is the way that the current flow?
What is conductor? What materials are good conductors?
What are insulators? What materials are good insulators?
What devices can generate an electric current?
What does a simple circuit consist of?
How does the current flow in the circuit?
What device can prevent filament from burning?
What is switch used for?
What appliances can be load?
What are the types of circuit arrangement?
What unit is the electric current measured?
What is voltage? What unit is voltage measured?
What is resistance? What unit is resistance measured?
What is Ohm’s law?
What are the methods of producing electrical energy?
How can current be produced by menace of EMF
What are rectifiers for? Where are they used?
What is the principle of rectifiers operation?
What parts does a rectifier consist of?
What is transistor?
What does this transistor contain?
What function does the transistor perform?
Where is the transistor used?
What are amplifiers used for?
What is the principle of amplifiers operation?
What are the components of a vacuum tube amplifier?
What parts does the transistor amplifier consist of?
