PRIMARY CELLS.

Chemical (источники) of an emf which (используются) for discharge only, thereby (превращая) chemical energy into electrical energy, (называются) primary cells. A simple primary cell consists of a containing jar (наполненный) with a solution of sulphuric acid as the

(электролит), a zinc plate and a cooper plate as ( электроды) . The most widely used primary cell of non-polarizing type is the Leclanche cell. It comprises a zinc and carbon electrode in a solution of ammonium chloride, often called sal ammoniac. The carbon (positive) electrode is packed in a (смесь) of manganese dioxide and carbon as a (деполяризатор).Also there are the storage cells. The distinction between an electric storage cell ( also called secondary cell or accumulator ) and a primary cell is that a storage cell after being discharged can be brought back to a full state of ( зарядка) by passing an ( электрический ток) through it. A lead storage cell consists of several negative and positive plates immersed in an electrolyte of (серная кислота) and (дистиллированная) water with a specific gravity of 1.08 to 1.21. The plates may be either of the Plante (formed) type or the Faure (pasted) type. There are two distinct types of (щелоч-ной) cells: the nickel-iron type and the nickel-cadmium type (the Russian type designations are ЖН и КН).

J. Revise the above texts and answer the following questions to them.

1. What is electrolysis?

2. What is the essence of Faraday’s first and second laws?

3. What is the form of a storage cell?

4. What does a lead storage cell consists of?

5. What is the construction of a simple primary cell?

6. What types of alkaline cells do you know?

K. Translate the following text from Russian into English, using new words.

K. Give the annotation of this text in Russian, learn all new words to improve your

vocabulary.

Incandescent (filament) lamps

Incandescent lamp was invented by Lodygin from Russia who demonstrated his invention in 1873, well before Edison. It consists of a filament which is highly refractory conductor mounted in a glass bulb. The filament is heated by the passage of an electric current through it to such a high temperature that it becomes incandescent and emits light.

To prevent rapid burning of the filament, the air is exhausted from the glass bulb, to form

a partial vacuum, hence the name vacuum lamp. Now incandescent lamps have filaments which are made of refractory metals such as osmium or tungsten. Heated to 2200 * C in vacuum lamps, the tungsten filament emits a brighter light, and consumes less energy. Such lamps have a very low luminous efficiency, only about 4 or 5 per cent of the electric energy consumed being converted to light, while the remainder is lost as heat.

Another group of lamps includes gaseous discharge lamps now widely used for decorative purposes, advertising, signs. These are mercury vapour, sodium vapour and neon lamps.

Another class of lamps embraces fluorescent lamps. It is a quartz tube filled with low-pressure mercury vapours. The inside of the tube is coated with a fluorescent powder, or phosphor, which converts the ultraviolet radiation of mercury discharge into visible light.

L. Make up your own reports on electrolysis, lamps, conductors, Joule’s law, Lodygin and

Edison. Get ready to discuss them with your group-mates.

Date: 2014-12-28; view: 1007