Structure of a vacuum tube triode.

In electronics, a vacuum tube, electron tube (in North America), thermionic valve, or just valve (elsewhere, especially in Britain), is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space, often tubular in form. Many devices called vacuum tubes are filled with low-pressure gas: these are so-called soft valves (or tubes); as distinct from the hard vacuum type, which have the internal gas pressure reduced as far as possible. Almost all depend on the thermal emission of electrons, hence thermionic.
Vacuum tubes were critical to the development of electronics technology, which drove the expansion and commercialization of radio broadcasting, television, radar, high fidelity sound reproduction, large telephone networks, modern types of digital computer, and industrial process control. Some of these applications pre-dated electronics, but it was electronics that made them widespread and practical; electronics have driven mechanical computers such as slide-rules to the point of obsolescence.
For most purposes, the vacuum tube has been replaced by solid-state semiconductor devices such as transistors and solid-state diodes: for most applications, they are smaller, more efficient, more reliable, and cheaper—either as discrete devices or as integrated circuits. However, tubes are still used in specialized applications: for engineering reasons, as in high power radio frequency transmitters; or for their aesthetic appeal, as in modern audio amplification. Cathode ray tubes are still used as display devices in television sets, video monitors, and oscilloscopes, although they are being replaced at various rates by LCDs and other flat-panel displays. A specialized form of the electron tube, the magnetron, is the source of microwave energy in microwave ovens and some radar systems.
A vacuum tube consists of arrangements of electrodes in a vacuum within an insulating, temperature-resistant envelope. Although the envelope is classically glass, power tubes often use ceramic and metal. The electrodes are attached to leads which pass through the envelope via an air tight seal. On most tubes, the leads are designed to plug into a tube socket for easy replacement.

Explanation:
The simplest vacuum tubes resemble incandescent light bulbs in that they have a filament sealed in a glass envelope which has been evacuated of all air. When hot, the filament releases electrons into the vacuum: a process called thermionic emission. The resulting negatively-charged cloud of electrons is called a space charge. These electrons will be drawn to a metal plate inside the envelope, if the plate (also called the anode) is positively charged relative to the filament (or cathode). The result is a flow of electrons from filament to plate. This cannot work in the reverse direction because the plate is not heated and does not emit electrons. This very simple example described can thus be seen to operate as a diode: a device that conducts current only in one direction. The vacuum tube diode conducts conventional current from plate (anode) to the filament (cathode); this is the opposite direction to the flow of electrons (called electron current).
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Answer the questions, based on the dialog above, and translate
the answers. Some answers will be found on the internet.

1. What is a vacuum tube, electron tube?
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2. How is the electric signal created?
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3. What are vavuum tubes filled with?
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4. How are they so-called?
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5. How is it distinct from the hard vacuum type?
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6. What do all these devises depend on?
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7. Vacuum tubes were critical to the development of electronics technology, because they drove the expansion and commercialization of what?
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8. What has the vacuum tube been replaced by?
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9. Where are Cathode ray tubes are still used as display devices?
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10. A specialized form of the electron tube, the magnetron, is still the sourse of what?
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11. What do the simplest vacuum tubes resemble?
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12. What do they have that makes them resemble light bulbs?
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13. What happends when it’s hot, and what does it realease, and how is the process called?
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14. What is the resulting negatively-charged cloud of electrons is called?
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History of development:

Write the correct present perfect tense of the verbs in parenthesis, to complete the paraghraphs.

The 19th century ______ __________ (saw) increasing research with evacuated tubes, such

as the Geissler and Crookes tubes. Scientists who ______ __________ (enperiment) with

such tubes and ______ __________ (include) Eugen Goldstein, Nikola Tesla, Johann Wilhelm

Hittorf, Thomas Edison, and many others.

Write the correct form of the verb “to be” and change the verbs in parentesis to the past tense to complete the paraghraphs.

These tubes ______ (be) mostly for __________ (specialize) scientific applications, or

______ (be) novelties, with the exception of the light bulb. The groundwork ______

(be) __________ (lay) by these scientists and inventors, however, this ______ (be) critical to

the development of vacuum tube technology.

Though the thermionic emission effect ________ (be) originally __________ (report) in 1873

by Frederick Guthrie, it is Thomas Edison's 1883 investigation of the "Edison Effect" that is more often mentioned.