Invention and history

British electrician William Sturgeon invented the electromagnet in 1825. The first electromagnet was a horseshoe-shaped piece of iron that was wrapped with a loosely wound coil of several turns. When a current was passed through the coil, the electromagnet became magnetized and when the current was stopped, the coil was de-magnetized. Sturgeon displayed its power by lifting nine pounds with a seven-ounce piece of iron wrapped with wires through which the current of a single cell battery was sent. Sturgeon could regulate his electromagnet; this was the beginning of using electrical energy for making useful and controllable machines and laid the foundations for large-scale electronic communications.

Introduction

The most fundamental type of electromagnet is a simple segment of wire (see figure). The amount of magnetic field generated depends upon the amount of electrical current that flows through the wire. In order to increase the effective current available to generate magnetic field, the wire is commonly configured as a coil where many segments of wire sit side by side. A coil forming the shape of a straight tube (similar to a corkscrew) is called a solenoid: a solenoid that is bent so that the ends meet is a toroid. Much stronger magnetic fields can be produced if a "core" of paramagnetic or ferromagnetic material (commonly soft iron) is placed inside the coil. The core concentrates the magnetic field that can then be much stronger than that of the coil itself.

Питання для самоконтролю:

1. When did British electrician William Sturgeon invent the electromagnet?

2. Could the scientist regulate his invention?

3. What is called an electromagnet?

Рекомендована література:

1. Гальперин И.Р., Медникова Э.М. Большой англо-русский политехнический словарь. – Москва: Русский язык, 1987.

2. ФедоршинО.П., Євстіфєєв П.Ф., Рябушенко Т.Л. Англійська мова. Практикум з науково-технічного перекладу, – Тернопіль Навчальна книга – Богдан, 2002 – 52с.

3. Чебурашкин Н.Д. Хрестоматия по техническому переводу. – Москва: Просвещение, 1987.

Дидактичне забезпечення: текст, словник.

13 Самостійна робота №13

Тема: Технічний переклад та переказ тексту за фахом: «Напівпровідникові катоди»

Завдання до самостійної роботи:

1. Скласти словник незнайомих слів.

Наприклад:

Слово	Транскрипція	Переклад
control grid	[`kontrəl grid]	керуюча решітка

2. Вивчити слова на пам'ять

3. Скласти анотацію англійською мовою (не менше 15 речень письмово)

4. Переказати текст згідно анотації.

“Semiconductor cathodes, anodes and others”

Semiconductor cathodes. This group includes the oxide-coated cathode, the one most widely used. The oxide cathode consists of a nickel or tungsten base coated with a layer of barium, strontium and calcium oxides. Oxide-coated cathodes have a lower electron work function and consequently a higher thermionic emissivity can be obtained at comparatively low temperatures (630 to 830°C).

Directly-heated cathodes. These cathodes are heated by passing current directly through them. In most cases filaments cannot be heated with alternating current. Due to a low thermal inertia, the temperature of this cathode changes periodically, causing corresponding variations in the emission current

Indirectly-heated cathodes. These cathodes consist of the cathode proper which emits electrons and the heater which provides the cathode working temperature.

Anodes. The anodes of the valve may be of cylindrical or rectangular configuration. They are made of nickel or another sheet metal such as aluminized steel and nickel. The grids are generally manufactured in the form of helixes of twisted tungsten, molybdenum, manganese nickel or alloys of nickel with molybdenium and tungsten. The required rigidity is obtained by welding the helix to suupports made of a thicker wire.

The electrodes are usually mounted in a stem of plane or comb configuration. The valve manufactured today have plane stems of small dimensions and short leads. Many designs of subminiatuie valves have no stem at all and the electrode leads are welded directly into the lower, flattened part of the envelope. Valves are evacuated through a special exhaust rube.

The Diode. Of the many types of tubes which are in use, the simplest is the diode or two electrode valve. This is a two-element valve which consists of an emitter of electrons (the cathode) and a collector of electrons (the plate or anode). The term 'diode" refers to the number of electrodes within the tube. The main function of the two - element tube is as converter of power. By this we understand that by means of the diode the electric power can be converted. Alternating voltage is converted in the form of pulsating direct current (the convertion of a, c. power into d. c. power). This is the process of rectification.

"The Triode. The triode, or three - electrode valve is an elaboration of the diode. The diode consists of two electrodes. They also appear in the triode and they constitute the basis of the triode. In the triode the third electrode (the control grid) is added in the space between the emitter*and the plate. The control grid is a metal structure which may be of different shape, depending upon the design of the tube. The basic function of the triode is to amplify the current, or voltage or electric power. In this process of amplification the control grid plays a most important role.

The Tetrode. A triode with an electrode placed between grid and anode is called a tetrode or four -electrode valve. This additional electrode is a screen grid. The screen grid surrounds the control grid using solid metal at top and bottom. The screen has a very small mesh compared with the control grid, ft had a profound effect on the characteristics of the valve (tube).

The Pentode. In the pentode valve an additional grid called the suppressor grid is placed between the anode and screening grid and is connected to the cathode either with the valve itself or externally. The suppressor grid greatly reduces the power of the screen grid to draw electrons from the vicinity of the anode, since electrons so placed will be attracted by the anode and repelled towards it by the suppressor grid.

Multigrid valves are also widely used. They are often used with two control grids simultaneously driven by a. c. voltages of different frequencies.