2015-08-21
650
1. Having improved this device they could use it for many purposes. 2. When making the experiment he made notes. 3. The vibrations of a voice speaking into the microphone of a telephone cause vibrations in an electric current. 4. This varying current is carried along a wire to a receiver. 5. Electronics has developed into hundreds of research institutes and laboratories employing tens of thousands of people. 6. Having been discovered many years ago this metal found a wide application in industry only last year. 7. While being checked the motor showed good performance. 8. The man introducing this famous scientist is the dean of our faculty. 9. Cybernetics is gaining a growing importance.
4. Translate paying attention to the ways of translation of -ed-forms .
A.
Early radios used crystal diodes to detect radio signals. These diodes allowed current to flow in one direction but not in the other.
B.
As electronics advanced, the design of the electron tube also progressed. Many of these advancements have resulted in a need for new kinds of diodes and triodes. And new elements have been added to the triode.
C. The Cathode
The directly heated cathode is a coated filament. The filament is often made of tungsten coated with thorium (this is called thoriated tungsten). The thorium acts as a good emitter of electrons when it is heated. The electrons emitted by the thorium are replaced by those emitted by the tungsten. The indirectly heated cathode consists of a metal cylinder heated by a filament placed inside. This type of cathode is usually coated with barium or strontium oxide.
5. Translate paying attention to the ways of translation of when+verb+-ed .
1. Certain materials emit electrons readily when heated. This is called thermionic emission. 2. When coated with a heat-sensitive material, the filament serves as a cathode and is called a directly heated cathode. 3. When placed in a vacuum tube, a plate does not receive electrons directly from the cathode. 4. When compared to the changes in Rp (place resistance), the AC plate resistance may be considered almost a constant for a particular triode. 5. When processed properly the substance acquires some new required properties. 6. The thorium acts as a good emitter of electrons when heated.
