XIII. Find active and passive forms of the verb in text 1 a. Write them out into two columns.

Active Voice	Passive Voice
has been transmitting … …	… was installed …

XIV. Read text 1 b. Find the answers in text 1 b to the following questions:

1. When was the early generator discovered?

2. How did the generator look like?

3. To what did the production of practical electromagnets lead?

4. What types of dynamos are known to you?

5. How do they differ from each other?

6. What are the major parts of generators and alternators?

7. Why do the rotors in large machines rotate at a high speed?

Text 1 b. Generators

Within a year of Michael Faraday’s discovery of electromagnetic induction (1831), a small hand generator was demonstrated in Paris, and by 1850 generators were being manufactured in several countries. These early generators were little more than assemblies of coils and permanent magnets that could be maintained in relative motion. Further developments of significance did not appear until the experimental work of William Sturgeon of England and of Joseph Henry and Thomas Davenport of the United States led to the manufacture of practical electromagnets. This technological advance contributed much to the development of practical electrical machines.

The dynamo-electric machines turn mechanical energy directly into electrical energy with a loss of only a few percent. There are two types of dynamos, namely, the generator and the alternator. The former supplies direct current (d. c.) which is similar to the current from a battery and the latter, as its name implies provides alternating current (a. c.).

To generate electricity both of them must be continuously provided with energy from some outside source of mechanical energy such as steam engines, steam turbines or water turbines, for instance.

Both generators and alternators consist of the following principle parts: an armature and an electromagnet. The electromagnet of a d. c. generator is usually called a stator for it is in static condition while the armature (the rotor) is rotating. Alternators may be divided into two types: (1) alternators that have a stationary armature and a rotating electro-magnet; (2) alternators whose armature serves as a rotor but this is seldom done. In order to get a strong electromotive force (e. m. f.), the rotors in large machines rotate at a speed of thousands of revolutions per minute. The faster they rotate, the greater the output voltage the machine will produce.

In order to produce electricity under the most economical conditions, the generators must be as large as possible. In addition to it, they should be kept as fully loaded as possible all the time.

XV. Make the plan of the given text.

XVI. Discuss the main points of your plan with a partner.

XVII. Skim over text 1c (See appendix, lang. Learn. Focus, p. 117). Give a better title for this text and prove your point of view. Text 1 c. Batteries

A battery is a simple device that converts chemical energy directly to electrical energy. It consists of two or more galvanic, or electrochemical, cells that produce direct-current electricity. The term battery is also commonly applied to a single galvanic cell. Every battery (or cell) has a cathode, or positive electrode, and an anode, or negative electrode. These electrodes must be separated by and are often immersed in an electrolyte that permits the passage of ions between the electrodes. The electrodes materials and electrolyte are chosen and arranged so that sufficient electromotive force (voltage) and electric current (amperes) can be developed between the terminals of a battery to operate lights, machines, or other devices. Since an electrode contains only a limited numbers of units of chemical energy convertible to electrical energy, it follows that a battery of a given size has a certain capacity to operate devices and will eventually become exhausted. The active parts of a battery are usually encased in a box (or jacket) and cover system that keeps air outside and the electrolyte solvent inside and that provides a structure for the assembly.

The first battery appears to have been constructed about 1800 by Alessandro Volta, a professor of natural philosophy at the University of Pavia in Italy. This device, later known as the voltaic pile, was composed of a series of silver and zinc disks in pairs, each of which was separated with a sheet of pasteboard saturated in salt water. A current was produced when the uppermost disk of silver was connected by a wire to the bottom disk of zinc. In 1836 the English chemist John Daniell developed what is considered the classic form of the voltaic cell.

Batteries are divided into two general groups: (1) primary batteries and (2) secondary, or storage, batteries. Primary batteries are designed to be used until the voltage is too low to operate a given device (flashlights, certain transistorized portable radios, electric razors, etc.) and then discarded. Secondary batteries consist of an assemblage of several identical voltaic cells. The lead-acid type of a secondary battery serves as the power source for the electrical systems of many kinds of motor vehicles, particularly automobiles and trucks.