Direct current generations and their applications

I. Read and learn the following words.

alternating/directзмінний/постійнийmeterвимірювальний прилад
current (a. c./d.c.)струмnucleus, nucleiядро, ядра
conductorпровідникoperating coilробоча котушка
electric chargeелектричний зарядpotential differenceрізниця потенціалів
electric circuitелектричне колоpowerпотужність, напруга
electromotive forceелектрорушійна силаunbranchedнерозгалужений
insulator, isolatorізоляторvoltageнапруга
ionіонto absorbпоглинати
in seriesпослідовноto consumeспоживати
matterречовина, матерія

II. Read and translate the text.

The essential difference between a d.c. generator and a. c. generator is that the former has a commutator by means of which the generated e. m. f. is made continuous, i. е., the commutator mechanically rectifies the alternating e. m. f. so that it is always of the same polarity. This is not, however, the only difference between them.

A d.c. generator as well as a motor of conventional type is made up of the following parts: outer frame, or yoke, pole cores, pole coils, armature windings, commutator, bruches, and bearings. Of these, the yoke, pole cores, armature core and the air gap between armature and pole core form the magnetic circuit while the pole coils, armature windings, commutator, and brushes form the electric circuit.

Generator fields may be either of two main types-separately excited or self- excited. The self-excited type is further, classified as series-wound, shunt-wound and compound-wound. In general practice compound-wound machines are used.

III. Answer the questions.

1.What forms of energy do you know?
2. Why electricity is the most important form of energy in modern technologies and everyday life?
3. What are the common sources of electric current?
4. What do you think are advantages and disadvantages of different forms of electric current, direct and alternating?
5. What are the main sources of electricity in this country?
6. What main rules of electric current do you know?
7. What types of measuring instruments are employed to fix damages in electric lines?

IV. Match the types of engineering with their meanings

1. Electronic engineering deals developing with...a) the prevention of the accidents, methods and procedures to safeguard workers in hazardous occupations. They assist designing machinery, factories, ships and roads, suggesting alterations and improvements
2. Computer engineering involves engineers in ...b) the field of design, test, build, and operate machinery of all types; they work on a verity of manufactured goods and certain kinds of structures.
3. Mechanical engineering is connected with...c) design and manufacture of memory systems, of central processing units, and of peripheral devices.Engineers try place greater and greater numbers of circuit elements onto smaller and smaller chips and increase the speed of computer operations.
4. Safety engineering has as its object ...d) the research, design, integration, and applications of circuits and devices used in transmission and and processing of information.

V. Fill in the gaps using the list of words below.

conductors current electromotive field direct alternative equipment electronic direction metals resistance apparatus solution carried ions positive

According to _________ theory, the electron is responsible for a flow of current of electricity. Good _________ are considered to be those substances in which there are present free electrons in constant but indiscriminate motion between the atoms. Under the action of an _________ force, these free electrons move in some definite direction, resulting in a constant stream of electrons flowing at a phenomenally rapid rate in the conductor. In the case a unidirectional or _________ current, this electronic stream is always in one direction, whilst with an _________ current the electronic stream reverses its _________ of motion with regular frequency. All pure _________ are good conductors of electricity, silver being the best since it offers the least _________ to a flow of current of electricity. We know copper to be very nearly as good a conductor as silver and, being very much cheaper, it is extensively used for electrical _________ of all kinds. It is universally employed in all aircraft electrical _________.

The conductor being a _________, say, of salt in water, the molecules of salt are ionized, both positive and negative ions moving under the influence of the electric field. In this case the sum of the quantities of positive and negative electricity, _________by the ions in a unit of time through any cross-section of the liquid, constitutes the electric current. Such a current is usually accompanied by a chemical action.

An electric current is carried through a gas only when the molecules or atoms of the gas are ionized. Here again, both the positive and negative _________ or electrons move under the influence of the electric _________, the sum of the quantities of _________ and negative electricity carried by the ions in a unit of time through any cross-section of the gas constituting the electric.