7. Make up the plan according to the text ( not less than 10 points).
Unit 15.
SEMICONDUCTORS
1. Read and translate the text:
CONDUCTORS, INSULATORS, SEMICONDUCTORS
Conductors are materials that have a large number of loosely bound valence-ring electrons; these electrons are easily knocked out of their orbit and are then referred to as free electrons. Insulators are materials in which the valence-ring electrons are tightly bound to the nucleus. In between the limits of these two major categories is a third general class of materials called semiconductors.
A semiconductor is a material with electrical conductivity intermediate in magnitude between that of a conductor and an insulator. This means conductivity roughly in the range of 103 to 10−8 Siemens per centimeter.
Semiconductor materials are the foundation of modern electronics, including radio, computers, telephones, and many other devices. Such devices include transistors, solar cells, many kinds of diodes including the light-emitting diode, the silicon controlled rectifier, and digital and analog integrated circuits. Similarly, semiconductor solar photovoltaic panels directly convert light energy into electrical energy. In a metallic conductor, current is carried by the flow of electrons. In semiconductors, current is often schematized as being carried either by the flow of electrons or by the flow of positively charged "holes" in the electron structure of the material.
Common semi conducting materials are crystalline solids, but amorphous and liquid semiconductors are also known. These include hydrogenated amorphous silicon and mixtures of arsenic, selenium and tellurium in a variety of proportions.
2. Remember the new words and expressions:
- conductors
- valence-ring electrons
- free electrons
- insulators
- nucleus
- major categories
- semiconductors
- electrical conductivity
- magnitude
- integrated circuit
- solar photovoltaic panels
- flow of electrons
- crystalline solids
3.Translate into English:
Провідник
Орбіта
Ізолятори
Напівпровідник
Електрична провідність
Потік електронів
Answer the following sentences:
Are conductors the materials that have a large number of loosely bound valence-ring electrons?
What are the insulators?
What do we call the semiconductors?
A semiconductor is a material with electrical conductivity intermediate in magnitude, is not it?
Where can we find the semiconductor materials?
Is current carried by the flow of electrons in a metallic conductor?
What common semi conducting materials do you know?
8. Describe the diagram. Name the parts of the structural scheme.
Unit 16.
TRANSISTORS
1. Read and translate the text: transistors
The transistor has become an important member of electronic devices and surpasses the vacuum tube in many applications in the electronic industry. The term "semi-conductor" means "half-conductor", that is a material whose conductivity is between that of conductors and insulators. They include such elements as silicon, germanium, selenium, phosphorus and others. The conductivity of semi-conductors increases with heating. Light as well as heat increases the conductivities of semi-conductors. Engineers and physicists see in them the way of solving many engineering problems. Converting heat' into electricity without using boilers is one of them. This could be done by means of the thermocouples made of semi-conductors.
Photocells made of semi-conductors are capable of transforming 10 per cent of sun-ray energy into electric power. The electricity produced by semi-conductor thermocouples can give not only heat but cold as well, on this principle refrigerators operate.