The Conception of Electrical Current

In the beginning of the 17^th century Sir William Gilbert discovered that many substances could be electrified by friction. Gilbert named this effect “electric” after the word “electron” – the Gr eek name for amber. In 1756 the great Russian scientist M.V. Lomonosov was the first to make theoretical analysis of electrical phenomena.

At present the nature of electrification was explained by the electron theory. According to the modern theory all matter is composed of atoms of tiny (крихітний) particles. There are many kinds of atoms. Each atom consists of a nucleus, a small positively charged mass and a number of lighter negatively charged particles called electrons, which revolve around the nucleus. Normaly each atom of a substance is electrically neutral, or it has equal amounts of negative and positive charges, i.e. produces no electrical effects. If the number of negative charges is not equal to the number of positive charge, the matter will produce electrical effects.

When the electrical charge is at rest it is spoken of as an static electricity, but when it is in motion it is referred to as an electric current. In most cases, an electric current is described as a flow of electric charges along a conductor. Not all substances are good conductors of electricity, whereas nonmetals are poor conductors. The poorest of conductors are commonly called insulators or non-conductors. There are a large number of substances that are neither good conductors of electricity nor good insulators. These substances are called semiconductors.

An electric current which flows in the same direction through a conductor or a current which does not change its polarity is called a direct current or a continuous current. Its abbreviation is (D.C.). An alternating current (A.C.) flows first in one direction and then in the other.

electric current

Conductor or a current which does not change its polarity is called a direct current or a continuous current. Its abbreviation is (D.C.) An alternating current (A.C.) flows first in one direction and then in the other.

An electric circuit is a path through which an electric current flows. This is a complete path along which electrons can transmit their charges. An electric circuit includes a battery, generator, or magnetic means for producing current flow. Some portion of the circuit is made to do useful work.

The circuit is said to be open when no charges can move due to a break in the path. The circuit is said to be closed when no break exist – when switches are closed and all connections are pro-perly made.

Special symbols are used to show electrical systems. There is a range of these symbols. There are some of them which are used when we draw circuits.

Electrical & electronic units table

Unit Name	Unit Symbol	Quantity
Ampere (amp)	A	Electric current (I)
Volt	V	Voltage (V, E) Electromotive force (E) Potential difference (Δφ)
Ohm	Ω	Resistance (R)
Watt	W	Electric power (P)
Decibel-milliwatt	dBm	Electric power (P)
Decibel-Watt	dBW	Electric power (P)
Volt-Ampere-Reactive	var	Reactive power (Q)
Volt-Ampere	VA	Apparent power (S)
Farad	F	Capacitance (C)
Henry	H	Inductance (L)
siemens / mho	S	Conductance (G) Admittance (Y)
Coulomb	C	Electric charge (Q)
Ampere-hour	Ah	Electric charge (Q)
Joule	J	Energy (E)
Kilowatt-hour	kWh	Energy (E)
Electron-volt	eV	Energy (E)
Ohm-meter	Ω∙m	Resistivity (ρ)
siemens per meter	S/m	Conductivity (σ)
Volts per meter	V/m	Electric field (E)
Newtons per coulomb	N/C	Electric field (E)
Volt-meter	V·m	Electric flux (Φe)
Tesla	T	Magnetic field (B)
Gauss	G	Magnetic field (B)
Weber	Wb	Magnetic flux (Φm)
Hertz	Hz	Frequency (f)
Seconds	s	Time (t)
Meter / metre	m	Length (l)
Square-meter	m2	Area (A)
Decibel	dB
Parts per million	ppm

Вправа 13. Виберіть правильні твердження.

1. Sir William Gilbert was the first to make theoretical analysis of electronical phenomena. 2. All matter is composed of atoms of tiny particles. 3. Normally each atom of a substance is electrically positive. 4. An electrical current is described as a flow of neutrons along a conductor. 5. The poorest conductors are commonly called insulators. 6. A current which changes its polarity is called a direct current. 7. An electric circuit is a path through which an electric current flows.

Вправа 14. Підберіть синонімічні пари.

Scientist, to revolve, matter, learned, nowadays, neutral, to give, substance, to make, to rotate, at present, thanks to, indifferent, to transmit, to produce, due to.

Вправа 15. Дайте відповіді на питання.

1. What was the first to make theoretical analysis of electrical phenomena?

2. What is all matter composed of?

3. What does each atom consist of?

4. What is an electrical current?

5. What is an alternating current?

6. What is an electric circuit?

Граматичний матеріал: Об’єктивний інфінітивний комплекс

Об’єктивний інфінітивний комплекс складається з двох частин. Перша частина комплексу – іменник у загальному відмінку або особовий займенник в об’єктному відмінку. Друга частина комплексу – інфінітив, що виражає дію. Яку виконує або якої зазнає особа або предмет, позначений іменником чи займенником, що стоїть перед інфінітивом.

На українську мову об’єктивний інфінітивний комплекс перекладається здебільше під-рядним додатковим реченням. Перша частина комплексу – іменник (займенник) - відповідає підмету підрядного речення, а друга – інфінітив – присудку.

Об’єктивний інфінітивний комплекс вживається після певних груп дієслів:

1) що виражають сприймання за допомогою органів чуття: to see, to hear, to feel, to watch, to observe, to notice. Після цих дієслів інфінітив у об’єктивному інфінітивному комплексі вживається без частки to. (She saw Mary cry – Вона побачила, що Мері плаче).

2) що виражають бажання, намір, почуття: to wish, to want, to desire, to like, to dislike, to hate, to intend, should/would like. (She wanted them to read that book. – Вона хотіла, щоб вони прочитали цю книжку).

3) що виражають думку (погляд), припущення, сподівання: to consider, to believe, to think, to find, to know, to expect, to suppose. (We consider him to be the best pupil of our school. - Ми вважаємо його найкращим учнем нашої школи).

4) що виражають наказ, прохання, дозвіл, пораду, примус: to order, to ask, to request, to allow, to permit, to advise, to recommend, to cause, to force, to make, to let. Після дієслів to make і to let інфінітив вживається без частки to. (We made George work – Ми примусили Джорджа працювати).

Виконання вправ на закріплення граматичної теми

Вправа 16. Перекладіть англійські прислів’я з об’єктивним інфінітивним комплексом.

1)You may lead a horse to the water, but you cannot make him drink. 2) Absence makes the heart grow fonder. 3) Each bird loves to hear himself sing.

Вправа 17. Прочитайте та перекладіть речення зверніть увагу на переклад інфінітиву.

1. He wants us to come to him today. 2. I would like you to wait for me here. 3. He wants his son to become anelectrician. 4. He wants to be sent to St. Petersburg to a conference. 5. She wants to be invited to a party. 6. We didn’t want to be interrupted. 7. Would you like me to help you? 8. I want his article to be published. 9. The doctor doesn’t want you to go to the south. 10. He wants the cargo to be insured. 11. She doesn’t like the children to do their home task in the evening.

Вправа 18. Перекладіть речення англійською мовою.

1. Він наказав водію зупинити машину. 2. Я попросив своїх друзів знайти статтю про змінний струм. 3. Я вважаю його своїм найкращим другом.

Заняття № 31

Тема: Джерела електричної енергії

Граматичний матеріал: Суб’єктивний інфінітивний комплекс

Вправа 1. Прочитайте та перекладіть лексику за допомогою словника.

pocket torch [ˈpɔkət ˈtɔ:tʃ]

power station [ˈpauə ˈsteɪʃən]

the nature of the method [ðə ˈneɪtʃə əv ðə ˈmeθəd]

primary cell [ˈpraɪˌmeriː ˈsel]

by purely chemical actions [ˈbaɪ ˈpjuəli ˈkemɪkəl ˈækʃənz]

moving through a magnetic field [ˈmuːvɪŋ ˈθruː ə mægˈnetɪk ˈfiːld]

across certain faces of a crystal [əˈkrɔs ˈsə:tən ˈfeɪsɪz əv ə ˈkrɪstəl]

as a means [əz ə ˈmiːnz]

for gramophone pick-ups [fə ˈgræməˌfoun ˈpɪk-ˈʌps]

through evacuated or gas-filled tubes [ˈθruː ɪˈvækjuˌweɪtɪd ər ˈgæs-ˈfɪld ˈtuːbz]

are liberated at the surface [ɑ: ˈlɪbəˌreɪtɪd ət ðə ˈsə:fəs]

by the action of light [ˈbaɪ ðiː ˈækʃən əf ˈlaɪt]

are driven from [ɑ: ˈdrɪvən ˈfrɔm]

by the impact of [ˈbaɪ ðiː ɪmˈpækt əf]

it may be pointed out [ɪt ˈmeɪ ˈbiː ˈpɔɪntəd ˈaut]