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.
Hi,
Is there any reason I should not use the 5VAC or the 6.3VAC taps on the power transformer and design a rectifier circuit to power a LED?
Thanks,
Billy
Be back in a bit
I'm having trouble finding any sources which describe how to accurately measure the contact angle between immiscible liquids in a tube. Any help would be appreciated.
Hello, I was curious about how to calculate how fast the escape velocity of hydrogen out of a tube/cylinder would be. Once end of the cylinder is closed, the other is open, obviously.
Assume the cylinder is full of hydrogen at 1 atm. My thought is that you could use PV=NRT to calculate the...
Hi y'all,
I am currently doing research in nuclear physics dealing with cryogenics. We want to pre cool the inner most part of a dewar with liquid nitrogen before we put liquid helium in since it's quite expensive. Once the nitrogen stops boiling off and reaches somewhat of an equilibrium, the...
Hey, working on something for a personal project and was wondering if you could point me in the right direction. I have a 47 inch hollow steel tube that I'm going to cut the end 6 inches into a half circle tube . I have a load of 200 lb at the top and am wondering how about I would quickly...
Hi,
Here is the schematic link: http://www.classictubeamps.com/schematics/Mesa/Mesa%20Boogie%20Solo%2050%20Rectoverb%20schematic.pdf
The 12AX7 inverter tube has a measured plate voltage of 416 VDC just like the schematic indicates.
V1a rail voltage is 394VDC with a 200K plate resistor and a...
Homework Statement
A light ray falls from the air (##n_a=1##) into the center of the upper surface of a long cilindrical glass tube with an index of refraction ##n_t=3/2##. The tube is submerged into water all the way to the upper edge and the waters index of refraction is ##n_w=4/3##. What is...
Consider 12 inches of 22 g twisted insulated copper wire with a 1 amp AC current at 6.2 volts.
The idea is to reduce the magnetic field effect on near by components.
Would placing this wire in a stainless steel tube reduce the magnetic field?
Can this be proven with a Gaussmeter? Note: I see...
Hi,
Here is a typical data sheet for a commonly used 6l6GC tube.
http://www.drtube.com/datasheets/6l6gc-jj2003.pdf
Under typical characteristics (in this data sheet) a value of Ra and Ra-a are given.
I assume Ra-a means Za-a and it could also be written as Zout. Is this a correct assumption...
Homework Statement
What 3 materials is the cathode coated with, from which the electron originate?
Homework Equations
None
The Attempt at a Solution
From what I managed to find, I think some may be nickel and barium but I'm not sure.
Homework Statement
[/B]Homework Equations
I honestly do not know any relevant equations for this relationship.
Well except f=v/2l.
The Attempt at a Solution
The only thing I could assume that it was was some sort of error , but I cannot find much material on the topic , so I was hoping to get...
Homework Statement [/B]
Suppose we have a u-shaped tube filled with water, with oil added at one end which disturbs the equilibrium. Now say one end is blocked off and the other is exposed to air flow which reduces the pressure above the water and causes the water to climb back to equilibrium...
Homework Statement
Homework Equations
Bernoulli's equation : ##P + \frac{1}{2}ρv^2 + ρgh ## = constant
The Attempt at a Solution
The pressure at the interface is ##P_{int} = P_0 + ρgH## .
Applying bernoulli's equation between point at the interface of two liquids and exit of the tube ...
For a hollow tube inside a hollow tube, with a pin passing through both and a force pushing down on the innermost tube, what would the bearing stress be on the holes (assuming tube wall thickness is equal)? Would the equivalent reaction force be F/4 since the pin is passing through 4 holes? So...
Homework Statement
(The question is in the image attached)
(c) An X-ray unit in the cardiac catheter labs has an output of 80µGy/mAs at 1 meter when the unit is set at 100 kVp. After adding 0.3mm Cu to the beam the photon intensity is reduced to a quarter and tends to vary in proportion to...
If wind was blowing through a tube at 15 kilometers an hour from an open end 2 meters wide to a tapered end only .3 meters wide how fast would the air be moving when it exits the pipe?
I'm using the equation Q = v * A (Q is flow, v is velocity and A is area of the tube opening) but is that the...
Homework Statement I[/B]
I am trying to find an equation that relates the velocity of 3 magnet when it falls down a copper tube to my measurement.
The length of the copper tube is L=0.24m,
The total mass of the 3 magnet is m = 4.98x10-3kg
magnetic flux density B = 428mT,
the thickness of the...
Hi,
I was wondering about the meniscus we get in a round tube, like a test tube or a boiling tube, or even a classic measuring cylinder. If we have a square transparent rectangle with water in - would this at all reduce the effect of the meniscus?
How else is the effect of the meniscus reduced...
Hi guys,
I was given this Mesa Boogie Nomad 45 chassis. I repaired it yesterday and have it working more or less well.
Mesa does not install adjustable bias in any of their amps. I want to install a trimmer pot to control the bias.
Where in the circuit should I place the trimmer resistor and...
I recently got an older tube amplifier , since ti was dirty from being left for a long time in an old shed i took the covers off and cleaned it , now I am listening it also with the covers off , everything works etc.
Now I wonder do tubes at lower voltages and lower frequencies such as in the...
Hi Guys,
I am having issues trying to repair this amp.
http://www.tangible-technology.com/schematics/fender/HR-Deville/Hot%20Rod%20DeVille.pdf
A little history is in order I guess. I have not been working on guitar amps for too long, several months now. I have repaired perhaps fifty or so...
1. The problem: A Geiger-Mueller tube is part of a Geiger counter, a device used to count the number of ionizing particles passing through it. It consists of a conducting outer cylinder held at zero electric potential with a thin central wire held at an electric potential of roughly 1000 volts...
Work output(deal) for a hydraulic machine per kg of incoming fluid is V(TANGENTIAL)*SPEED OF BLADE (assuming zero out swirl velocity.
Draft tube causes static pressure ont runner outlet to fall below zero. Thus available head is increased by an amount equal to this drop. But power output from...
Hello there!
I'm new on the forum and english is not my first language.
I'm working on an art project and I wonder if there's any mean by which I can transport the light from an illuminated scene across a small tube (let say not larger than 5 cm in diameter) and over some distance (let say 2...
For a gas generator like this, I have seen diagrams of the thistle tube in the water, below the other tube or above it, where is it meant to be?
Also, where is the other tube meant to be because I have seen it in multiple positions.
Thanks!
"For a particular flow rate, the pressure drop due to the downward flow of the fluid is
balanced by the pressure gain due to gravity—that is, at this flow rate, the static
pressure in the pipe is independent of the distance along the pipe."
Book says this. Can you explain how the pressure...
Hello,
first of all, I understand, how microwave tube works but I'm interesting in how exactly the microwave heat up a things? What's the matter inside. I have heard about increasing energy of molecules of water by polarization them by micro-wave. But I have got a plate which is not from...
Homework Statement
A cathode ray tube (CRT), consisting of an electron gun and a screen, is placed within a uniform constant magnetic field of magnitude B such that the magnetic field is parallel to the beam axis of the gun, as shown in figure...
Homework Statement
vertical glass tube with height of 2H. H is 760mm.
the lower half is full of an unknown gas. the upper half is full of mercury.
The gas gets heated so it pushes the mercury out of the glass tube.
What temperature must the gas be heated to?
here is the photo if, for some...
Homework Statement
A horizontal Pitot tube (with one end open for airflow and another closed) is accidentally installed into an airplane askew, so that the tube is not horizontal. Instead the closed tube end is higher (in the y-direction of a xy-plane) than the inlet end. How does this affect...
An unfortunate incident happened at our triple effect caustic evaporator (32w.t% to 51w.t%). The third effect (highlighted red) where major steam (~12-13bar depending on flowrate) assisted evaporation take place, here for some reason Ni tubes get severely collapsed, while the plant was offline...
Homework Statement
Hi,
I'm a junior doctor. It's been so long since I had physics!
I've question about tube that's placed in chest cavity to drain air/fluid/etc.
The second bottle, is under-water seal bottle.
I know that its purpose is to prevent air moving TO the patient. but how?
The "trap...
Homework Statement
Basically, the goal of the "project" is to find the equation for oscillation of a "fractionless" fluid in a v-shaped tube, regarding the angle. I know how to solve the same problem regarding a u-shaped tube, but in this case, I can't figure out where to place the angle in the...
Homework Statement
Water flowing at the rate 3.5 kg s−1 through a tube with an inner diameter of 2 cm is to be heated from 20 to 40◦C. If the tube wall temperature is maintained at 90◦C, determine the length of the tube required.
Homework Equations
Q'=Cp*m*(DeltaT)
Q=2*pi*r*L*Q'
The Attempt...
I have just learned about the cathode ray tube in the class room. There is a part called electron gun in it which emits electrons and these electrons finally strike the fluorescent screen.(I hope its correct till here.) But I want to ask that won't there be a loss of electrons in this process...
I understand, from my textbook, that certain frequencies of sound (depending on the length of the tube) will reflect off the interface between the air in the tube and the air outside, that this interface is a discontinuity.
But in all other cases where discontinuities caused (partial)...
Hello,
Normally a pitot tube points in the direction of airflow so that it measures static and dynamic airflow. If it points in the opposite direction my assumption is that it will not measure the dynamic pressure but will only measure the static pressure.
Is this correct?
Hi, I need some advice on what steel tubing to go for. I have either 65x35x2mm or 50x25x2mm.
The steel tube is 2.4M & stays in upright/vertical position, with an extended 40cm long piece horizontal on top holding some weight between 30-40KG for some time.
I would like to go the 50x25x2mm as...
Homework Statement
A solenoid is placed beneath a CRT that produces a magnetic field of 1.10 x -2. The CRT is 1 meter away from a screen.
The electrons that make up the beam were accelerated from rest through a potential difference(V) at the beginning of the CRT. Acceleration of the electrons...
Homework Statement
A U-shaped tube of uniform section "S" has one extreme closed and the other one open to the atmosphere. The tube contains mercury (M) in the central part, a gas (G) to the left that exerts a pressure "p" and a column of water (W) of height h_w to the right. Then, a mass "m"...
If atmospheric pressure hot and cold air are sent into the opposing sides of a vortex tube (the ports normally used for gas outlet), will compressed air be generated/released from the hole/port normally used for gas input?
The reverse of the system above (cold and hot air enter from opposing...
Hello everyone, I'm in the process of building a flow bench to test cylinder heads. What I'm after is to make a pitot tube to measure port velocity. Any help would be appreciated. Thanks
For my year 12 physics EEI (extended experimental investigation) i need to develop some sort of experiment with variables i can change to retrieve data from. I have a basic cathode ray tube from a few months ago much like the one in this video: . Does anyone have any idea of what variables i...
Hey guys.
It's been a long time since I've done anything beyond a simple shear stress calculation, so have what will hopefully be a basic question.
I've found similar examples but not ones I was confident I could apply to mine.
As per the dodgey paint sketch I've made below, I have this...
For a physics problem, I need to calculate the solid angle subtended by an oblique cone (cone where the apex does not lie on the line perpendicular to the cone's base from the center of the base).
Consider the following problem:
I have a 2D disk which emits light in an ever growing hemisphere...