What is Tube: Definition and 883 Discussions

A vacuum tube, electron tube, valve (British usage) or tube (North America) is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.
The type known as a thermionic tube or thermionic valve uses the phenomenon of thermionic emission of electrons from a hot cathode and is used for a number of fundamental electronic functions such as signal amplification and current rectification. Non-thermionic types, such as a vacuum phototube however, achieve electron emission through the photoelectric effect, and are used for such purposes as the detection of light intensities. In both types, the electrons are accelerated from the cathode to the anode by the electric field in the tube.
The simplest vacuum tube, the diode, invented in 1904 by John Ambrose Fleming, contains only a heated electron-emitting cathode and an anode. Electrons can only flow in one direction through the device—from the cathode to the anode. Adding one or more control grids within the tube allows the current between the cathode and anode to be controlled by the voltage on the grids.These devices became a key component of electronic circuits for the first half of the twentieth century. They were crucial to the development of radio, television, radar, sound recording and reproduction, long-distance telephone networks, and analog and early digital computers. Although some applications had used earlier technologies such as the spark gap transmitter for radio or mechanical computers for computing, it was the invention of the thermionic vacuum tube that made these technologies widespread and practical, and created the discipline of electronics.In the 1940s, the invention of semiconductor devices made it possible to produce solid-state devices, which are smaller, more efficient, reliable, durable, safer, and more economical than thermionic tubes. Beginning in the mid-1960s, thermionic tubes were being replaced by the transistor. However, the cathode-ray tube (CRT) remained the basis for television monitors and oscilloscopes until the early 21st century. Thermionic tubes are still used in some applications, such as the magnetron used in microwave ovens, certain high-frequency amplifiers, and amplifiers that audio enthusiasts prefer for their "warmer" tube sound.
Not all electronic circuit valves/electron tubes are vacuum tubes. Gas-filled tubes are similar devices, but containing a gas, typically at low pressure, which exploit phenomena related to electric discharge in gases, usually without a heater.

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  1. H

    Designing reflector straight line lamp

    Who can help me to calculated a reflector for a straight light tube with a diameter of 6mm and a length of 300mm given a beam with a width of 100mm at a distance of 500-700mm?
  2. Albo

    Exit velocity of gas through two orifices

    If a gas flowing through a tube would meet two orifices with different diameters in the same cross section, how much of the gas would flow through each orifice and what would the gas velocity be in dependence of orifice diameter?
  3. Eitanburg

    Help finding the right material for non-conductive tubing

    Hi, I need a tube that will be shatter proof, non conductive for electricity and be a good heat insulator, it need to be rigid and sustained high temperature (~250 c°)
  4. E

    Density of Flow Along a Tube Under the Action of Advancing Piston

    I'm trying to figure out how describe the mass of air between the piston face and the und of the tube ( position ##o##) in the acompanying diagram. At ##t = 0##, the mass of air in the tube is ##M_o##, and the system is static with tube length ##l##. The ##x## coordinate describes how far...
  5. C

    Speed of sound from resonant length of tube vs tuning fork wavelengths

    The graph is, I do not understand why how it is possible to find the speed of sound from the gradient for this graph. Can someone please help? Many thanks!
  6. G

    How to wind a 5K audio tube amplifier transformer?

    60 watt tube amp needs a 5k primary and 8 ohm secondary transformer. I have wound voltage transformers on my lathe many times. Audio transformer is no different. Online impedance transformer calculator says, 5k to 8 ohms in 25:1 ratio. Online info says, audio transformer should be 60w x 5 =...
  7. D

    Creating turbulence in a small tube

    I have an odd question or a project I have been bouncing around in my head and I want to make sure that I am understanding the science of it all correctly. My question is will this cause turbulence in the larger chamber so that the air from the Yellow Question mark area is being pulled and mixed...
  8. S

    I What is the most efficient way to cool air using a Vortex Tube (Ranque-Hilsch)?

    Ref: https://s3.wp.wsu.edu/uploads/sites/44/2015/12/VortexTubeOptimizationTheory.pdf The above paper says that the initial separation of hot and cold air is complete once the flow is partly deflected backwards at the left hand side (HOT) end. See Fig. 1 in the paper. It also says that the...
  9. Rezex124

    Experiment - how temperature changes along a tube, using heaters

    TL;DR Summary: Help needed with plotting heat maps, using data we gathered in an experiment. Hello, so I'm having problems with analysing data, which we gathered from an experiment we did in class. This is meant as a type of non-guided experiments class, where we are just given an initial...
  10. M

    I Coil Around A Tube - Iron Cylinder Inside Tube - How Many Turns Needed?

    Hello, I am wanting to wrap a coil of wire around a tube, suspend an iron cylinder in the tube, energize the coil, and have it be able to suspend around 500 pounds on the iron cylinder. I was playing around with some online calculators for coils, and didn't really get anywhere, so I figured I...
  11. arhg

    A Normal force and force of friction inside a tube

    Dear all, Me and some colleagues (non-physicists) are discussing how force works when passing a cylinder (which we are holding) into a narrow tube. As we insert more of the cylinder into the tube, the force we are exerting is increasing. My theory is that the normal force is increasing and his...
  12. sumatoken

    Study of harmonic motion of a liquid in a V shaped tube

    A V-shaped tube with a cross-section A contains a perfect liquid with mass density and length L plus and the angles between the horizontal plane and the tube arms as shown in the attached figure. We displace the liquid from its equilibrium position with a distance and without any initial...
  13. C

    Help for bending calculation rectangular steel tube

    Hi all In order to make a metal preframe for a French window as an entrance door, I began to estimate the possibility of building it in rectangular steel tubes of 100 x 50 x 3 mm, laid independently of the walls that could not accept such a load because it was timber framed. The preframe will...
  14. J

    I GM tube and dual probe scintillator

    Recently I measured a range of sources with two detectors comparing their efficiency. One of the sources used (C-14) was a pure beta emitter and it made me wonder. If a radioactive source decays by beta then gamma, will one decay register as two counts as two radioactive particles are produced...
  15. O

    Flux density help please (seawater flowing in a tube)

    What is the flux density of salt in a horizontal tube 10 cm in length connecting seawater (salinity = 30 g/l) to a tank of freshwater (salinity ~ 0) assuming no advection occurs?
  16. sol47739

    I Postive rays in cathode ray tube experiments?

    I read in the following book A history of the sciences by Stephen F. Mason. About the discovery of the electron the write what I attached in the picture. I wonder what do these positive rays traveling in the opposite direction they talk about consist of? Some ions or what? I understand that the...
  17. O

    I Why are the spectral lines weak in my hydrogen Geissler tube?

    Using a hand spectroscope, I looked at the spectrum of two geissler tubes, helium and hydrogen. The helium spectrum is what I expected, dominated by five distinct lines. The hydrogen spectrum, however, is somewhat disappointing. It is dominated by an almost continuous spectrum, it is not evident...
  18. soothsayer

    Gas conductance through tube at low pressure

    I have a vacuum chamber of volume V connected to a vacuum pump via a tube of radius R and length L, and I want to design this "tube" such that R can be controlled in order to provide a constant rate of pressure change inside of the chamber of 2.5 mbar/sec, from atmosphere down to ~0.5mbar...
  19. maistral

    Confusion: outer tube heated vs. inner tube heated

    Hi, I'm rather confused with the wording in Perry's Chemical Engineers' Handbook regarding "outer tube heated" and "inner tube heated" in double-pipe heat exchangers. Obviously both are opposites of each other, so I'd like to ask using "outer tube heated" as reference. When we say "outer tube...
  20. samy4408

    I Question about X-ray power emitted by the Coolidge tube

    hello i found this equation in a course about x rays , and i couldn't find it anywhere else they said that it is the theoretical expression of the energy spectrum , and dφ/dE is variation of the power emitted by the Coolidge tube as a function of the energy of the x ray. but i didn't understand...
  21. CPW

    Intermediate Axis Theorem.... fun to learn it again with You Tube

    A friend of mine shared a YouTube video with me, saying he was sure I would love it. He described it as very strange with a rotating wingnut in the space station flipping over on its rotation axis, over and over, while it spun rapidly. After watching the video, I verified I was taught the...
  22. P

    I Calculate the internal pressure of a tube based on flow rate

    I have pump of unknown flowrate pumping water through a tube of length L and diameter D. I know that the flowrate of water exiting the tube is X mL/min. I would like to know the internal pressure of the tubing, how can I calculate it? This all occurs at sea level elevation.
  23. A

    RF tube with photocathode, photoinjector

    https://dspace.mit.edu/bitstream/handle/1721.1/95319/97ja001_full.pdf;sequence=1 In most (all?) RF tubes from klystron to magnetron to TWT and I assume also the gyrotron they use a DC accelerating field and a thermionic cathode with constant emission. The RF signal then gets introduced and it...
  24. F

    Will a 4x4 Steel Tube Fail Under 35-40,000 lbs?

    Have a lifting yoke with 7/8 inch lifting eyes welded onto the ends of a 3/16 or 1/4 inch wall 4x4 a500 or a513 square steel tube. Expected UDL is as much as 35-40,000 lbs. Is this tube going to fail?
  25. FEAnalyst

    Corrugated tube (bellow) under axial load

    Hi, I'm trying to verify the results of a finite element analysis of a corrugated tube (bellow) subjected to axial load. Here are my analytical calculations based on Roark's Formulas for Stress and Strain (originally the formulas are from the article "On the Theory of Thin Elastic Toroidal...
  26. D

    I Behaviour of electrons in a teltron tube

    If I switch off the anode voltage in a teltron tube (used to determine the charge-to-mass-ratio of the electron), the visible electron beam disappears. Why is this so? The electrons, which were already shot out of the electron gun before, have a high velocity and should continue to move on a...
  27. physicslover2012

    Standing Waves in a tube closed at both ends

    During our classes, we haven't discussed the situation of a tube closed at both ends. But, assuming the position of the nodes and antinodes, I think it's a case similar to the one where the tube is open at both ends, so I think that f = v/λ = nv/(2L). Using the numeric data, my frequency would...
  28. Kawana87

    Tongue weight capability of 2x3x.125 steel tube at 21"?

    Hello everyone. I'm building myself a half-rack for weight lifting that included 2 overhung support beams above from which to hang a safety strap incase of a failed lift. They are made from 2x3x.125 steel tube (they're Oriented with the 3" vertically). The tube are overhung by 21". How much...
  29. D

    Lessons with electron beam deflection tube and teltron tube

    Hello, I would like to discuss with my students the deflection of electrons in electric and magnetic fields. For this purpose, I would like to perform the experiments with electron beam deflection tubes and teltron tubes. How would you implement this organizationally in the classroom? There are...
  30. R

    Correct Parametrization for Calculating Area of a Tube?

    Hi, I'm trying to find the area of this tube using ##\int \int ||\vec{N}|| ds d\theta##. However, I get 0 as result which is wrong. So at this point, I'm wondering if I made a mistake during the parametrization of the tube. This is how I parametrized the tube. ##S(s, \theta) = (cos(s), sin(s)...
  31. Iwanttolearnphysics

    About KE and PE of a stone falling down a tube filled with oil

    This question does not have numbers, so I'm stumped. Here's my thinking. (I), the gain in KE is less than the loss in GPE is correct according to the key, but I think I don't understand this conceptually. Can you ask me questions to make me think about this a bit more? I can't even form...
  32. T

    I Calculating Torque for 100 Ton Steel Tube Press

    I have a problem, I need to calculate the torque required to rotate a steel tube 150mm OD, 90mm ID which is being pressed against a identical tube with a force of 100 Tons also the estimated torque imparted if the above parts come into contact with one part static and the second part rotating at...
  33. T

    I Bouncing Height of Cylindrical Tube: Equation & Properties

    What is the equation to find the bouncing height of a cylindrical tube when the flat surface is falling on the floor under Earth's gravity? I know the mass, drop height and material properties of the cylindrical tube.
  34. abdulbadii

    How to make hard metal toolkit handle from Polyethylene tube

    How do we make hard metal toolkit handle from high density Polyethylene tube/pipe inside which the tool near end is united, glued by some material (black as seen for now, try to give pic. later on)
  35. J

    3D Laplace solution in Cylindrical Coordinates For a Hollow Cylindrical Tube

    Here is the initial problem and my attempt at getting Laplace solution. I get lost near the end and after some research, ended up with the Bessel equation and function. I don't completely understand what this is or even if this i the direction I go in. This is a supplemental thing that I want to...
  36. L

    Mass m sliding without friction inside a rotating tube

    1) To be in equilibrium, it must be $$\begin{cases}F_{centr}-T=0\\ T-mg=0\end{cases}\Rightarrow F_{centr}=T=mg\Rightarrow m\omega^2 R_0=mg\Rightarrow R_0=\frac{g}{\omega^2}$$ 2) It is intuitive that this equilibrium is unstable but I don't know how to formally prove this. 3) In ##R_0## the...
  37. S

    Diesel Injector and Water Tube Boiler Back-Pressure

    Diesel injector: How much pressure relative to the maximum combustion chamber pressure during the sharpest phase of detonation does an injector need to be able to overcome to inject its full charge? How much overlap is typical between injection and detonation? Water-tube boiler: Are the water...
  38. Johan M

    EDF Rocket with Thrust Tube: Physics Explained

    Hi everyone. I am tasked with making an EDF rocket for a university project. The end of the rocket has a set of flaps that redirect air to control the rockets trajectory, seen in the image. The 90mm EDF itself is located near region 1.. I would like to know why, the physics behind it, a smaller...
  39. G

    Does Poiseuille's Law apply for vertical motion of fluids down a tube?

    I investigated the flow rate of differing dilutions of glycerol through an orifice of a vertical tube and obtained the following: I'm looking for a way to quantify these results so looked to Poiseuille's Law; I'm pretty sure my graph does not show inverse proportion? Could anyone advise me as...
  40. NSNS

    How to find maximum load on steel sqare tube

    how to find a maximum load on a steel square tube that has one fixed end to the wall and another end is hanging free. suppose the beam is 2230 mm long and the load is applied on the beam on the free end w= 1040 mm. but there also a steel square tube that welded to the middle of the beam and...
  41. T

    Ion flow through a charged tube

    Suppose we have a charged metal tube through which charged ions of compressible fluid is passing. I want to know whether the boundary layer will still form that will resist the flow or the flow will be smoother. We all know how strong electromagnetic force is and this will push the ions away...
  42. P

    Investigating the Sound Reflector of a Gas Inlet Tube

    My theory is that the gas inlet end, which is supposed to act as a sound reflector may not be doing a great job because it is plastic and has a hole cut in the centre for the gas inlet port. But by that reasoning, the flames at the end most distant from it (the sound inlet end) should be the...
  43. P

    Will painting a tube black cool it down?

    My thinking is that a paint coating will slow down heat loss due to an insulation effect, but at the same time speed up radiative heat loss from the outside black paint surface. I am unsure though which effect may be the greatest and therefore the net effect on tube temperature. Many thanks
  44. Limebat

    I Does combusted gas travel faster in a vacuum tube?

    Hey all, So if a gas is combusted, would it travel faster through a vacuum tube or a regular ole' tube? I would assume the vacuum tube, as there are less particulates collisions in the way of the fast-moving gas molecules. Yet this also implies pressure on the outside of the thin barrier _ 2...
  45. S

    Position of speaker in front of tube to produce stationary wave

    That is part of the article. I want to ask about step 4. I know the basic theory of how stationary wave is formed (superposition of incoming and reflected wave) and also basic concept about stationary wave in open and closed tube, something like this: But I don't know the reason why in step 4...
  46. hutchphd

    FYI : Tube Robot Looks Really Useful

    Perhaps this is old news but that would be self-descriptive. How long has this been around? I want to build one today. .
  47. J

    Finding change in height of fluid in U tube from change in T

    So first I converted the density from g/cm^3 to kg/cm^3 (it wants the answer in cm). This gives me a density of 0.01356 kg/cm^3. Then I thought about the relationship of pressure and temperature. Since volume remains constant and temperature is the only variable changing, the change in pressure...
  48. J

    Finding pressure of gas in u shaped tube with liquid

    The answer is suppose to be 0.9432. Initially I thought the pressure inside the glass ball would just be the same as the atmospheric pressure because these equal pressures would cancel each other out, but obviously that's not true. I can calculate the density of the gas using the equation...