U-tube Definition and 51 Threads

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. A

    Fluid Heights in an Open U-Tube

    Pressure on side with liquid 1 = ##p_0 + \rho_1gh_1## Pressure on side with liquid 2 = ##p_0 + \rho_2gh_2## The solution sets the two pressures equal. I am confused how the two sides have the same amount of pressure, one would have more than the other.
  2. P

    Forces at the bottom of a rotating U-tube filled with water

    So when the rotation starts some water will move upwards and in the vertical part of tube. I know hat centripetal force will be given by F=mv²/r Now I though of taking r as centre of mass of the water system but I don't know what to take the value of m as? Should I only consider the water...
  3. brotherbobby

    Pressure due to two liquids in a U-tube

    (a) Situation (2) is my answer (which cannot be in static equilibrium). The pressures in the lower dashed line (##P_2##) has to be the same on either side (for equilibrium). That means the pressure due to the red liquid is equal to the pressure due to the same length of air column (length)...
  4. MattGeo

    I Question about a u-tube manometer with different diameters

    Let's suppose that a water filled u-tube is open to the atmosphere at one end and at the other end it is capped and evacuated. Suppose also that the diameter of the capped evacuated end is drastically larger than the open end. (Ignore effects of boiling or vapor pressure). Would the much larger...
  5. Avimanyu Ray

    Pressure not matching at same height in a U-tube

    Can we please look at the following attached file image? It shows a utube filled with a little water and the rest is oil. Thus, the height of oil in one arm will be more than the height of water in the other. When we compare the pressure at the height of the surface of water with that...
  6. Nikhil Rajagopalan

    Is Pressure Constant in U-Tube Arms with Different Density Liquids?

    A liquid in a U-tube maintains the same level in both the arms. When another liquid which does not mix with the first one is poured in it, the air interface with either of the liquids in both the arms will be at different levels. Considering a point at the top surface of liquid A, the pressure...
  7. H

    Fluid Statics- u-tube displacement

    Homework Statement A uniform U-tube is partially filled with water (ρH20 = 1000 kg/m3). Oil, of density 750 kg/m3, is poured into the right arm until the water level in the left arm rises 30 mm. The length of the oil column is then: (Answer: 40mm) Homework Equations P = pgh Pressure = density...
  8. H

    Pressure-related problem with Mercury and Water in a U-tube

    Homework Statement Mercury is poured into a U-tube as shown in Figure a. The left arm of the tube has cross-sectional area A1 of 11.0 cm2, and the right arm has a cross-sectional area A2 of 4.60 cm2. One hundred grams of water are then poured into the right arm as shown in Figure b. The length...
  9. A

    Work done by gravity on fluid in u-tube.

    Homework Statement Two cylinders of base area 4cm2 hold fluid of density 1.30(103). In one the fluid has height .854 and the other has height 1.560. They are then joined and the fluids equalize in height--find the work done by gravity on the fluid. Homework Equations A version of...
  10. A

    U-Tube (Pv=nRT, Pascals) Problem

    Challenge problem 1. Homework Statement A U-tube of uniform cross section contains mercury. The initial temperature of the system is 301K and the barometric pressure is 749 torr. Suppose the left side of the tube is closed at the top and the temperature is raised to a temperature such that...
  11. D

    What is the effect of applied pressure on a partially filled U-shaped tube?

    Homework Statement A U-shaped tube is partially filled with water. One end of the tube is then capped so that the air in that end is trapped (initially at atmospheric pressure). The tube has a bore diameter of 10mm. The initial height of the entrapped air gap is 200mm. A gauge pressure of 1500...
  12. P

    Two liquids are inside of a U-tube, which

    Homework Statement Two containers are connected with a u-tube as shown above. An steady equilibrium state is reached where oil with a density of ##900\frac{kg}{m^3}## exactly fills the left leg connected to the container with pressure ##p_1## and the other other leg is filled with water. What...
  13. Q

    Find the height of fluid in a U-tube container?

    Homework Statement A block of mass 20 g sits at rest on a plate that is at the top of the fluid on one side of a U-tube as shown below. The U-tube contains two different fluids with densities ρ1 = 1070 kg/m3 and ρ2 = 650 kg/m3 and has a cross sectional area A = 4.6 * 10-4 m2. The surfaces...
  14. M

    What Is the Period of Oscillations in a U-Tube with Varying Radii?

    Homework Statement A U-tube has vertical arms of radii r and 2r, connected by a horizontal tube of length l whose radius increases linearly from r to 2r. The U-tube contains liquid up to a height h in each arm. The liquid is set oscillating, and at a given instant the liquid in the narrower...
  15. R

    Liquid oscillating in a U-tube problem

    Homework Statement A U-tube has vertical arms of radii 'r' and '2r', connected by a horizontal tube of length 'l' whose radius increases linearly from r to 2r. The U-tube contains liquid up to a height 'h' in each arm. The liquid is set oscillating, and at a given instant the liquid in the...
  16. X

    U-tube filled with water and inmiscible liquid

    Homework Statement A U-shaped tube is partly filled with water and partly filled with a liquid that does not mix with water. Both sides of the tube are open to the atmosphere. If h1 = 0.52 m and h2 = 0.16 m, what is the density of the liquid? Homework Equations ρ_{u}=h_{1}/h_{2} *...
  17. T

    The period of water oscillating in a U-tube

    In the following lecture (starting at 21:00), the professor says that when predicting the period of water oscillating in a U-shaped tube, that the "length" of the water column that you should use should be greater than the average of the length around the outside and around the inside. Can...
  18. Darth Frodo

    Finding the Height of a Heavy Oil Column in a U-Tube with Mercury and Light Oil

    Homework Statement U-tube has mercury of relative density 13.6. Column of light oil is poured into one limb. It is 15 cm tall and of relative density 0.78. A column of heavy oil is poured into the other limb so that it is level with the top of the light oil column. Find the height of the heavy...
  19. Darth Frodo

    Hydrostatics: U-Tube Homework Solution

    Homework Statement A u-tube of uniform cross section with vertical limbs of height 20cm has mercury of relative density 13.6 in the bottom of it. The columns of mercury in each limb are 6.9cm high. Water is poured into one limb until it just reaches the top. Find the height of the water...
  20. I

    U-tube manometer fluid mechanics

    Hi friends - I'm at a lost on this particular problem which reads: a manometer consists of a U-tube, 7mm internal diameter, with vertical limbs with an enlarged upper end of 44mm diameter. the left-hand limb and the bottom of the tube are filled with water and the top of the right hand limb...
  21. S

    How to Calculate Fluid Height in a U-Tube Using Bernoulli's Equation

    Homework Statement The following tube has dimensions d1=1.13 cm and d2=3.60 mm. Air (density = 1.28 kg/m3) flows through the tube at a rate of 1131.0 cm3/s. Assume that air is an ideal fluid. What is the height h of mercury (density = 13600.0 kg/m3) in the right side of the U tube...
  22. T

    Calculating Rise of Mercury in U-tube with Water

    Homework Statement A simple open U-tube contains mercury. When 12.3 cm of water is poured into the right arm of the tube, how high above its initial level does the mercury rise in the left arm? Homework Equations density of water=1000kg/m^3 density of mercury=13534 kg/m^3 The...
  23. N

    How to Derive the Oscillation Period of Water in a U-Tube?

    Homework Statement Consider a column of liquid (density ρ) of length ℓ confined in a U-tube of uniform cross-sectional area A. Suppose that the water level on one side is pushed down a small amount and then released. 1) Construct expressions for the potential and kinetic energies of the...
  24. A

    How Does Adding a Lighter Liquid Affect Water Displacement in a Modified U-Tube?

    Figure 14-32 shows a modified U-tube: the right arm is shorter than the left arm. The open end of the right arm is height d = 10.0 cm above the laboratory bench. The radius throughout the tube is 1.30 cm. Water is gradually poured into the open end of the left arm until the water begins to flow...
  25. D

    U-Tube Mass and Pressure Problem

    1. A U-tube is filled with water, and the two arms are capped. (Intro 1 figure) The tube is cylindrical, and the right arm has twice the radius of the left arm. The caps have negligible mass, are watertight, and can freely slide up and down the tube. 2. The locations of the two caps at...
  26. M

    U-tube with Equilibrium Configuration

    Homework Statement A U-tube of uniform cross-sectional area, open to the atmosphere, is partially filled with mercury. Water is then poured into both arms. If the equilibrium configuration of the tube is as shown in the figure, with h2 = 1.51 cm, determine the value of h1. I'm not...
  27. U

    How Does Bernoulli's Equation Determine the Height of Mercury in a U-Tube?

    [SOLVED] Bernoulli's equation & U-Tube Homework Statement Air flows through this tube at a rate of 1200 cm^3/s . Assume that air is an ideal fluid. What is the height of mercury in the right side of the U-tube? Homework Equations Bernoulli's Equation (P1 + 1/2*rho*V1^2 +...
  28. P

    Pressure in u-tube of mercury with added water

    Homework Statement A simple open U-tube contains mercury. When 11.8 cm of water is poured into the right arm of the tube, how high above its initial level does the mercury rise in the left arm? Hint: At the level of the interface between the water and the mercury, the pressure on the left...
  29. D

    Height of Block on U-Tube: Calculations & Results

    Homework Statement A block of mass 20 g sits at rest on a plate that is at the top of the fluid on one side of a U-tube as shown below. The U-tube contains two different fluids with densities ρ1 = 1090 kg/m3 and ρ2 = 595 kg/m3 and has a cross sectional area A = 4.7 10-4 m2. The surfaces are...
  30. L

    How Is Fluid Pressure Calculated in a U-Tube Experiment?

    1. The locations of the two caps at equilibrium are now as given in this figure. (Part D figure) The dashed line represents the level of the water in the left arm. What is the mass of the water located in the right arm between the dashed line and the right cap? 3. p - p_0 +rho*g*d...
  31. T

    What Height of Water in a Long Arm Risks Popping the Seal?

    Homework Statement The plastic tube has a cross-sectional area of 5.00 cm². The tube is filled with water until the short arm (of length d = 0.800 m) is full. Then the short arm is sealed and more water is gradually poured into the long arm. If the seal will pop off when the force on it...
  32. S

    Solving Pressure in U-tube with Different Densities

    Homework Statement Two liquids A and B of densities 1.0 g cm-3 and 0.8 g cm-3 are poured into an U-tube as shown in the figure below. Find x ! Homework Equations P = \rho g h The Attempt at a Solution Is it possible liquid A is on top of liquid B because A has higher density than...
  33. R

    Mercury & Water Flow in U-Tube: Determining the Length & Height

    Mercury is poured into a U-tube. The left arm of the tube has cross-sectional area A1 of 10.0 cm2, and the right arm has a cross-sectional area A2 of 5.00 cm2. One hundred grams of water are then poured into the right arm.(a) Determine the length of the water column in the right arm of the...
  34. C

    U-tube Mercury: Pressure and Height Calculations with Pumped Right Side

    Homework Statement The u-tube shown has a cross-section of 1 cm^2. It contains mercury to the shown levels. The pressure above the the mercury is 750 torr. The left side is sealed off. The right side is is pumped such that the pressure is approximately zero. i) Determine the far the mercury...
  35. J

    Finding the period of oscillation of a u-tube w/ water (almost solved)?

    Homework Statement Using the energy method( setting potential energy= kinetic energy) show that the natural period of oscillation of the fluid in a u-tube manometer is t=2PI(l/2g)^(1/2) where L is the length of the fluid column. 2. The attempt at a solution So as you can see I do not...
  36. H

    U-tube: Water Rises Slightly - Get Help on the Right Track

    Homework Statement A person blows across the top of one arm of a U-tube partially filled with water. The water in that arm...? The answer is rises slightly: The water in that arm rises slightly. I really couldn't figure out why. Could someone help get me on the right track?
  37. J

    Heights of fluids in a u-tube?

    Homework Statement Glycerin is poured into an open U-shaped tube until the height in both sides is 36 cm. Ethyl alcohol is then poured into one arm until the height of the alcohol column is 30 cm. The two liquids do not mix. What is the difference in height between the top surface of the...
  38. K

    How Is Potential Energy Calculated in an Oscillating U-Tube with Varying Radii?

    Hi, Just wondering if anyone has any thoughts on how to approach this question: A U-tube has vertical arms of radii 'r' and '2r', connected by a horizontal tube of length 'l' whose radius increases linearly from r to 2r. The U-tube contains liquid up to a height 'h' in each arm. The liquid...
  39. K

    How Does Oscillating Liquid in a U-Tube Calculate Potential Energy?

    Hi, Just wondering if anyone has any thoughts on how to approach this question: A U-tube has vertical arms of radii 'r' and '2r', connected by a horizontal tube of length 'l' whose radius increases linearly from r to 2r. The U-tube contains liquid up to a height 'h' in each arm. The...
  40. M

    Pressure Difference: U-Tube Manometer w/ 825kg/m^3 Fluid

    Homework Statement A U-tube manometer contains a fluid with density of 825 kg/m^3. The difference in height of the two columns is 35cm. What is the pressure difference?Homework Equations None?The Attempt at a Solution I have no bloody clue. I'm sure I've done this before in AP Chem, but right...
  41. K

    Difference in liquid column heights in a rotating U-tube

    Homework Statement A U-shaped tube with a horizontal segment of length L contains a liquid. What is the difference in height between the liquid columns in the vertical arms if the tube is mounted on a horizontal turntable, and is rotating with angular speed w, with one of the vertical arms...
  42. M

    Conceptual Pressure Question: Fluid Pressure in a U-Tube

    Homework Statement A U-tube is filled with water, and the two arms are capped. The tube is cylindrical, and the right arm has twice the radius of the left arm. The caps have negligible mass, are watertight, and can freely slide up and down the tube. A one-inch depth of sand is poured onto the...
  43. P

    Help Me Solve My Problems: U-Tube and Styrofoam Bucket

    I really suck at these problems. I don't know what I'm doing wrong. Please help. 1. A U-tube contains liquid of unknown density. An oil of density 785 kg/m3 is poured into one arm of the tube until the oil column is 15 cm high. The oil-air interface is then 7 cm above the liquid level in the...
  44. W

    What is the Height of Each Fluid in the U-Tube Arm with Oil-to-Water Ratio of 4?

    Consider a U-tube whose arms are open to the atmosphere. Now water is poured into the U-tube from one arm, and light oil (p=790 kg/m^3) from the other. One arm contains 70 cm high water, while the other arm contains both fluids with an oil-to-water height ratio fo 4. Determine the height of each...
  45. M

    Solving U-Tube Fluid Problem: h1 Calculation

    The problem is; “Mercury is poured into a U-tube. The left arm of the tube has cross-sectional area A1 of 10.0cm^2, and the right arm has a cross-sectional area A2 of 5.0cm^2. 100 grams of water are then poured into the right arm. (a) Determine the length of the water column in the right...
  46. A

    Determining Height of Mercury in U-tube: Air Flow Rate of 1200 cm^3/s

    Ok, Air flows through this tube at a rate of 1200 cm^3/s. Assume that air is an ideal fluid. What is the height h of mercury in the right side of the U-tube? Here's a picture: http://session.masteringphysics.com/problemAsset/1001181/6/knight_Figure_15_64.jpg First, I found the velocity of...
  47. J

    Fluid Mechanics - U-tube and mercury

    A U-shaped tube, open to the air on both ends, contains mercury. Water is poured into the left arm until the water column is 20.0 cm deep. How far upward from its initial position does the mercury in the right arm rise? So far, this is my work: Using pressure = density(water) x g x...
  48. P

    Electric Potential in Insulated U-Tube

    Hey, I have this question, and I'm having quite a bit of difficulty figuring it out. "An insulating rod is bent into a semicircular arc of radius a, and a total electric charge Q is distributed uniformly along the rod. Calculate the potential at the center of curvature of the arc if the...
  49. J

    How does air blowing over a u-tube affect the heights of water and oil columns?

    I really need help on this problem. I've been stuck forever A U-TUBE AT BOTH ENDS IS PARTIALLY FILLED WITH WATER. OIL (DENSITY = 750KG/M2) IS THEN POURED INTO THE RIGHT ARM AND FORMS A COLUMN L=5.00 CM HIGH. DETERMINE THE DIFFERENCE h IN THE HEIGHTS OF THE TWO LIQIUD SURFACES. THE RIGHT ARM...
  50. S

    Gas Pressure in Open-End U-Tube Manometer

    1) What is the pressure in a gas container that is connected to an open-end U-tube manometer if the pressure of the atmosphere is 752 torr and the level of mercury in the arm connected to the container is 8.60 cm higher than the level of mercury open to the atmosphere? a. 666 mm Hg...
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