vacuum tube.?

Question

What are vacuum tubes?
How do they function?

Can sbdy explain the "vacuum" part of it?

Basic and intuitive way to understand..?

Thanks guys!!
Could sbdy also explain the 'tube' part of it..

Answer 1

Vacuum tubes are electrical devices that are used to modify electrical current, like transistors and other electronic components. They are the early versions of transistors and other devices, actually. They plugged in to circuit boards. They took a while to heat up before they could do what it was they did, which is why early radios, TVs, and other devices took a few minutes to start working. The reason they are called vacuum tubes is because they are a sealed glass tube that has the air sucked out of it and then is sealed, creating a vacuum inside of it. There is lots of information on them on the web that tells what different types do. Too much to list here. Try Wikipedia first.

http://en.wikipedia.org/wiki/Vacuum_tube

Answer 2

Back before there were integrated circuits, or even transistors, everything electronic worked with vacuum tubes. The basic idea is that there's an electric current (a stream of electrons) traveling through a vacuum (air would block the flow) from the cathode (negative terminal) to the anode (positive terminal). Between these is a screen, called the grid. Varying the voltage on the grid varies how much current passes through the tube. In practice there might be additional elements to improve performance. To greatly simplify things, if you wanted to make an amplifier to play music, you put the music signal on the grid voltage, and it would control the current through the tube, which then powers a speaker.

A small AM radio might take six or eight tubes of various types. When the radio stopped working, you would open it up, pull out all the tubes, and take them down to the shop, where they had a tube tester. You plugged in each tube in turn until the tester identified the bad one. Then you bought a new one and put the radio back together. Tubes were quickly replaced by transistors as soon as cheap transistors became available. Transistors were smaller, cheaper, more reliable, and used less power. Some high-end audio equipment still uses vacuum tubes because they give a warmer tone to the music.

Answer 3

A vacuum tube triode is a transconductance device; a voltage controls a current. Essentially, within a vacuum bulb, a cathode is heated (directly or indirectly) such that electrons are 'boiled' off (thermionic emission). Surrounding the cathode is a metal cylinder called the plate


SOURCE
S32750 Super Duplex tube fitting

Answer 4

The most basic function to explain is a diode which consists of an anode (+) and a cathode(-) these are the thingys you see sticking up inside the tube.

The cathode has allot of electrons that want to jump across to the anode when voltage is applied. It is easier for these electrons to jump across when there is no air to interfere, so that is why the air is sucked out of vacuum tubes. There are many configurations that were used but in short they were used to control voltages much the same way transistors do.


Hope this helps. I wonder what made you ask?

Answer 5

Vacuum tubes are the predecessors of transistors. The 'vacuum' part means the insides of it are in a space perhaps 99.44% free of any atmosphere. This is required for the filaments to survive from heating up from the current passing through them. If there was any air in the tube, the filaments would just immediately combust and destroy themselves. Edison discovered this when he was attempting to build the first working light bulb. The simplest vacuum tube is called a diode. This link should help.: http://en.wikipedia.org/wiki/Vacuum_tube#Diodes_and_triodes

Answer 6

there are many different types of vacuum tubes. they have functions ranging from that of a diode (only allowing electricity to travel in one direction) to signal amplifiers (like the tubes found in old guitar amplifiers) to that of transistors, like the tubes in the old computers.

the "vacuum" part is because they are vacuum sealed. The simplest tubes have a filament like a regular light bulb. It heats up and begins to release electrons, causing the space inside the tube to become negatively charged. These electrons are then attracted to the slightly positively charged anode plate in the vacuum tube. If they weren't vacuum sealed, the gas inside would become ionized and allow easy transmission of electrical current, causing erratic behavior.

computer vacuum tubes functioned as diodes and relays to create logic gates, but were eventually replaced by transistors.

Answer 7

Vacuum tubes change electronic signals. They look pretty much like light bulbs.

They are called "vacuum" tubes because the pressure inside is less then the pressure outside - this is called a vacuum.

Not sure I can explain how they work. Try the reference.

Answer 8

Tube amps require output transformers because what comes out is wrong for driving the coils in the speakers. And of course it is not DC - it is music which is by definition alternating - sine wave mixes. Microwaves use, I believe, a single tube, the klystron that actually produces the microwaves. The rest is solid state. When transistor amplifiers were introduced, they were praised for their crisp clear sound and precise feed back of the recorded material. But people then discovered that the recorded material included stuff they didn't really want to hear - like mouthing instruments and clicks on the stage - and people divided into those that wanted cleaner recordings and those that preferred the "warm" sound of tubes which covered up the perfect errors.

Answer 9

Vacuum tube consists of inner tube,outer tube,selective absorbing coating,vacuum sandwish,getter,getter film and spring holder.
Sunlight is absorbed by the selective absorbing coating and converted to heat energy,and then heat energy heat water in the tube.