VII. Put a subordinate clause according to model

Model: -When rubbing a piece of amber, the ancient people made it attract light materials.

-When the ancient people were rubbing a piece of amber, they made it attract light materials.

1. When connected direct across the brushes, the field coils have the full voltage of the mains.

2. When found in Free State, metals were widely used by primitive man.

3. When speaking about the problems of utilizing solar energy, we should stress their aim.

4. When considering the chemical properties of metals, we must mention that they vary widely in the degree of chemical activity.

5. If told in detail, the principle of operation of this machine is rather simple.

VIII. Express the main idea of the text.

IX. Answer the questions.

1. What is a generator?

2. What is the function of a motor?

3. What has the generator?

4. What are the essential parts of a generator?

5. When are the D.C. generators used?

6. When are the large D.C. generators used?

7. When are the Generators of small capacities used?

Практическая работа № 23 magnetism

Цель: Введение и активизация лексики по теме «Магнетизм».

Оборудование: комплект тестов, раздаточный материал, иллюстрации по теме

	Vocabulary I. Learn the words and expressions.
to employ	использовать
the list	список
starting motor	стартер
ignition coil	катушка зажигания
horn	гудок
cutout relay	предохранительное реле
windshield wiper	дворник (электр.)
a conductor	проводник
to intensify	усиливать
the form of a coil	форма спирали
the insertion	ввод, вставление
iron core	железный стержень
to be stored	накопляться
to be converted	превращать
to be transformed	преобразовываться

II. Read and translate the text. Magnetism

Most of the electrical units in a car employ not only electricity but also magnetism (produced by electricity) to make them work. The list of electromagnetic units includes the starting motor, generator, ignition coil, horn, horn relay, solenoids, cutout relay, current regulator, voltage regulator, electric wind shield wiper and so forth.

For some reason, whenever an electron is in motion, a magnetic field surrounds that electron. Likewise, whenever an electric current flows through a conductor, a magnetic field surrounds that conductor. This total field is the sum of the fields surrounding all the electrons flowing through the wire. Therefore, the intensity of the field is proportional to the amperage.

The force of an electro-magnet is concentrated and intensified by making the wire into the form of a coil, called solenoid. The strength of the field is proportional to the number of amperes flowing through the coil times the number of turns in the coil. The lines of force in the magnetic field are still further concentrated by the insertion of an iron core. Solenoids with iron cores are used to open and close relay switches. Generator and motor armatures and field poles, and ignition coils are solenoids with iron cores. All solenoid cores are made of soft iron or soft steel so they will lose practically all their magnetism as soon as solenoid circuit is broken.

The magnetic field represents electric energy which is stored in magnetic form. When the solenoid circuit is first closed, the current rises to a maximum. During this time some of the energy in the current is converted into magnetic energy and stored as such in the field surrounding the solenoid. When the solenoid circuit is broken, the magnetic energy is transformed back into electric energy in the solenoid and a spark may jump across the switch points while they are being opened.