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Give Russian equivalents of the following phrases.
Ordinary gases, the dominant source of electrical conduction, a relatively small number of mobile ions produced by radioactive gases, dielectrics or insulators, free electrons, avalanche breakdown, number of mobile electrons and positive ions, a light emitting conductive path, by high temperature, in response to an electric field, the bulk of the current.
2. Complete the sentences.
1.The dominant source of electrical conduction is via a relatively small number of mobile ions produced by…2. Since the electrical conductivity is extremely low, gases are …3. . A plasma can be formed by high temperature, or by application of …4.The electrons in a plasma accelerate more quickly in response to an electric field…
Put questions to the following sentences.
1. The breakdown process forms a plasma that contains a significant number of mobile electrons and positive ions, causing it to behave as an electrical conductor. 2. Plasma is the state of matter where some of the electrons in a gas are stripped or "ionized" from their molecules or atoms. 3. A plasma can be formed by high temperature, or by application of a high electric or alternating magnetic field as noted above.
Retell the text.
Text 21: Vacuum.
Vocabulary
1. emission – распространение
2. exceed –превышать
3. thermionic emission -
4. ejection – выбрасывание
5. generate – производить
6. incandescent – накаленный добела
7. cathode –катод
8. sustained –подпирающий
9. explosively –взрывной
10. a vacuum arc forms – вакуумные электродуговые формы
Since a "perfect vacuum" contains no charged particles, vacuums normally behave as very good insulators. However, metal electrode surfaces can cause a region of the vacuum to become conductive by injecting free electrons or ions through either field emission or thermionic emission. Thermionic emission occurs when the thermal energy exceeds the metal's work function, while field emission occurs when the electric field at the surface of the metal is high enough to cause tunneling, which results in the ejection of free electrons from the metal into the vacuum. Externally heated electrodes are often used to generate an electron cloud as in the filament or indirectly heated cathode of vacuum tubes. Cold electrodes can also spontaneously produce electron clouds via thermionic emission when small incandescent regions (called cathode spots or anode spots) are formed.
These are incandescent regions of the electrode surface that are created by a localized high current flow. These regions may be initiated by field emission, but are then sustained by localized thermionic emission once a vacuum arc forms. These small electron-emitting regions can form quite rapidly, even explosively, on a metal surface subjected to a high electrical field. Vacuum tubes and sprytrons are some of the electronic switching and amplifying devices based on vacuum conductivity.