Учебные задания по английскому языку для студентов 2 курса направления бакалавриата «Электроэнергетика и электротехника» 4 семестр

quality of daylight. In addition, the efficiency of the fluorescent lamp is high. A fluorescent tube taking 40 watts of energy produces as much light as a 150-watt incandescent bulb. (4)________________, fluorescent lamps produce less heat than incandescent bulbs for comparable light production.

One advance in the field of electric lighting is the use of electroluminescence, known commonly as panel lighting. In panel lighting, particles of phosphor are suspended in a thin layer of nonconducting material such as plastic. This layer is sandwiched between two plate conductors, one of which is a translucent substance, such as glass, coated on the inside with a thin film of tin oxide.

(5)________________, an alternating current is passed through the phosphor, causing it to luminesce. Luminescent panels may serve a variety of purposes—for example, to illuminate clock and radio dials, to outline the risers in staircases, and to provide luminous walls. The use of panel lighting is restricted, however,

(6)__________________.

A number of different kinds of electric lamps have been developed for such special purposes as photography and floodlighting. These bulbs are generally shaped to act as reflectors (7)_______________. One such lamp is the photoflood bulb, an incandescent lamp that is operated at a temperature higher than normal to obtain greater light output. The life of these bulbs is limited to 2 or 3 hours, as opposed to that of the ordinary incandescent bulb, which lasts from 750 to 1000 hours. Photoflash bulbs used for high-speed photography produce a single high-intensity flash of light, (8)_________________, by the ignition of a charge of crumpled aluminum foil or fine aluminum wire inside an oxygen-filled glass bulb. The foil is ignited by the heat of a small filament in the bulb. Increasingly popular among photographers is the high-speed gas-discharge stroboscopic lamp known as an electronic flash.

A. With the two conductors acting as electrodes,

B. which is coated on the inside with a fluorescent material known as phosphor, C. Because of this illuminating power,

D. if an electric current is passed through them, E. when coated with an aluminum mirror,

F. which is employed for decorative sign and display lighting,

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G. making a magnificent impression,

H. because the current requirements for large installations are excessive,

I. lasting a few hundredths of a second.

VOCABULARY PRACTICE

1.Give Russian equivalents to the words and word combinations in bold.

2.Complete the text with words formed from the words in capitals.

RADIATION

3. Write out the passage using one of the words from the list.

Luminescence is the (1)_______of light by means other than combustion and therefore (2)_______at lower temperatures than are required for combustion. An example of luminescence is the light, or glow, emitted by a luminous watch dial. Luminescence contrasts with (3)________, which is the production of light by heated materials.

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When certain materials (4)_______various kinds of energy, some of the energy may be emitted as light. This process involves two steps: (a) the (5)________energy causes the electrons of the atoms of the absorbing material to become (6)_______and jump from the inner orbits of the atoms to the outer orbits; (b) when the electrons fall back to their original state, a photon of light is (7)_______. The interval between the two steps may be short or long. If the interval is short, the process is called fluorescence; if the interval is long, the process is called phosphorescence. In either case the light produced is almost always of lesser energy, that is, of longer wavelength, than the exciting light.

Fluorescence and phosphorescence have a number of (8)________ applications. The picture (9)_______in television receivers are coated with fluorescent materials known as phosphors that (10)______when excited by a cathode ray. The interiors of fluorescent lamps have similar (11)________, which absorb the invisible but (12)_______ultraviolet components of the primary light source and emit visible light. A special type of fluorescence called (13)_______emission occurs in the operation of

alaser.

4.Put each verb in brackets into a suitable verb form.

FLUORESCENT LAMPS

A fluorescent lamp (1)______(consist) of a phosphor-coated tube, starter, and ballast. The tube (2)_____(fill) with an inert gas (argon) plus a small amount of mercury vapor. The starter (3)______(energize) the two filaments when the lamp first

(4)_____(turn on). The filaments supply electrons (5)_____(ionize) the argon,

(6)______(form) a plasma that (7)______(conduct) electricity. The ballast

(8)_____(limit) the amount of current that can (9)_____(flow) through the tube. The plasma (10)_____(excite) the mercury atoms, which then (11)_____(emit) red, green, blue, and ultraviolet light. The light (12)_____(strike) the phosphor coating on the inside of the lamp, which (13)_____(convert) the ultraviolet light into other colors. Different phosphors (14)_____(produce) warmer or cooler colors.

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5. Complete the passage with a suitable preposition in each space.

IONIZATION

Ionization consists ___ the formation ___ electrically charged atoms or molecules. Atoms are electrically neutral; the electrons that bear the negative charge are equal ___ number ___ the protons ___ the nucleus bearing the positive charge. When sodium combines ___ chlorine, ___ example, to form sodium chloride, each sodium atom transfers an electron ___ a chlorine atom, thus forming a sodium ion

___ a positive charge and a chloride ion ___ a negative charge. ___ a crystal of sodium chloride the strong electrostatic attraction ___ ions ___ opposite charge holds the ions firmly ___ place and close together. When sodium chloride is melted, the ions tend to dissociate because ___ their thermal motion and can move about freely. If two electrodes are placed ___ molten sodium chloride and an electric potential is applied, the sodium ions migrate ___ the negative electrode and the chloride ions migrate ___ the positive electrode, causing a current ___ electricity to flow. When sodium chloride is dissolved ___ water, the ions are even more free to dissociate (because ___ the attraction between the ions and the solvent), and the solution is an excellent conductor ___ electricity.

SPEAKING

Make a presentation on a particular type of lamp.

MODULE IV

ASSESSMENT

Translate from English into Russian.

The earliest experiments in electric lighting were conducted by British chemist Sir Humphry Davy, who produced electric arcs and who also made a fine platinum wire incandescent in air by passing a current through it. Beginning about 1840 a number of incandescent lamps were patented. None were commercially successful, however, both because the vacuum pumps of the time could not create a vacuum strong enough to protect the wire filaments and because electricity was expensive to obtain. In 1878 and 1879, British inventor Joseph Swan and American inventor

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Thomas Edison simultaneously developed the carbon-filament lamp. Improved vacuum pumps and the increased availability of electricity made these lamps a success. During the same period various arc lamps were introduced. The first practical arc lamp was installed in a lighthouse at Dungeness, England, in 1862. The American pioneer in electrical engineering Charles Francis Brush produced the first commercially successful arc lamp in 1878. Tungsten filaments were substituted for carbon filaments in incandescent lamps in 1907, and gas-filled incandescent lamps were developed in 1913. The fluorescent lamp was introduced in 1938.

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