What is Thermal: Definition and 1000 Discussions

A thermal column (or thermal) is a column of rising air in the lower altitudes of Earth's atmosphere, a form of atmospheric updraft. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example of convection, specifically atmospheric convection. The Sun warms the ground, which in turn warms the air directly above it. A thermal is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically.

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  1. J

    A multiple concept problem thermal expansion/stress

    Hi guys! I think I need to explain myself before I ask for the advice :) I'm 27 (so been in grade 12 ages ago) - I didn't have science, I wrote it years later. Now I'm enrolled for a Bsc degree in the hope of getting into medical school (very tough in South Africa). I'm putting a lot of time...
  2. G

    What Temperatures Contribute to Air's Heat Capacity Due to Vibration?

    Homework Statement Air is mostly composed of diatomic nitrogen, N2. Assume that we can model the gas as an oscillator with an effective spring constant of 2.3 x 103 N/m and and effective oscillating mass of half the atomic mass. For what temperatures should vibration contribute to the heat...
  3. S

    BEC condenstate thermal statistics vs. coherence

    Hi. I'm reading an introductory section on the Bose-Einstein condensation of a non-interacting, spinless boson gas. I'm confused by the claim that the ground state is in a coherent state with eigenvalue sqrt(N0) exp(i theta), where N0 is the expected number of particles in the ground state. The...
  4. D

    Thermal mass, building shell air volume, and heat losses over time

    Hello, I'm looking for some feedback on and an analysis of a spreadsheet calculator I've made. It looks at temperature changes over time, given starting volumes of a building shell and thermal mass. The calc takes into account building fabric and ventilation heat losses. First I've...
  5. V

    Effective thermal conductivity of sintered bronze

    Hi I've been trying to find effective thermal conductivity of sintered bronze, especially of that used in self-oiled sliding bearings (like Oilite). I need it to know how much less it is compared to dense copper alloys, eg. tin bronze. So far my search has proven fruitless. It seems that...
  6. S

    Insulation Most Relevant for a Fridge

    Homework Statement So you have a fridge, the walls of the fridge are made of aluminum, plastic and insulation. Which is the most relevant and why for the fridge. Homework Equations Thermal conductivity of aluminum=250 Plastic=.03 insulation=0.035 - 0.16 The Attempt at a Solution...
  7. J

    How to calculate Laws of Thermal Radiation

    1. Star X has a surface temperature of 10,000 K. How much power does it emit per square meter? Enter numbers only. Do not enter units (watt/m2 is assumed) 2. Star X has a surface temperature of 10,000 K. What is the wavelength of the dominate electromagnetic radiation that Star X emits? Enter...
  8. A

    What's Left to Discover in Chemical and Thermal Physics?

    Are there any major questions yet to be solved in these fields? Also where exactly does thermodynamics, heat fit into physics?Thermal Physics?
  9. S

    Thermal conductivity conceptual

    Homework Statement So the outside of a refrigerator is made up of plastic, metal, and insulation? Which is the most important and why. Homework Equations no equation needed. The Attempt at a Solution I thought that the insulation would be the most important because it reduces...
  10. P

    Measurement of material displacement using recorded material thermal data

    Hello all I am trying to measure material displacement using measured thermal data.7 While the specimen is heated up, I want to measure how much it changes its length at particular points. Is this possible? If you have any further questions or suggestions please do not hesitate to...
  11. S

    Thermal Conductivity: Exploring the Disparity in the Real World

    Homework Statement I was wondering why there is such a disparity between thermal conductivty and how they act in the real world. Ex. If if have 3 cups filled with hot water. The 3 cups are made of glass, plastic and metal. The metal will obviously have way higher thermal conductivity...
  12. S

    Is work done by friction the same as thermal energy?

    Homework Statement I ask this because my initial assumption was that work done by a non-conservative force (friction in this case) is also equal to thermal energy. However, in my book, it gave an equation with W = Emec + E thermal. They also had an example where they added up the work and...
  13. K

    Thermal Neutron Capture from 55Mn to 56Mn

    Homework Statement In a reactor, we're making 56Mn by inducing thermal neutron capture. 2g sample of 55Mn is put into the reactor which has a flux of thermal neutrons of 3E13 neutrons/cm^2*s Sample is in the reactor for 8 hours and then removed. a. Calculate the amount and activity of...
  14. 1

    Thermal Physics Problem: Determining Volume & Cp/CV for Ammonia Gas

    [b]1. Determine the volume occupied by a 1 mole of an ideal gas at 27° C and 1 atm pressure. Ammonia gas at 27° C and 1 atm is passed at a rate of 41 cm3 s-1 into an apparatus where it flows over an electrically heated wire of resistance 100 . When the heating current is 50 mA the gas leaves...
  15. S

    Why Do Different Materials Affect Temperature Change in Containers?

    Homework Statement Hi so i have a few questions on thermal properties, the questions are supposed to be conceptual with no calculations. 1. There are 3 containers. They are made of plastic, glass and alluminum. If you put hot water into the 3 containers, why is there is small difference in...
  16. S

    Thermal stability vs melting point

    An ionic compound is more thermally stable when the metal cation is more reactive. So its harder to decompose. But then what's the difference between melting and decomposition? Also, when an compound is harder to decompose, does it mean its melting point is higher? Because even though Na2O...
  17. J

    Thermal expansion: Plastic Molding

    Homework Statement ABS plastic melts (and solidifies) at 105 °C. You want to inject it into a steel mold. When the part comes out at 20°C you want it to be 7.250cm long. Edit: If this isn't clear, it wants to know how big the steel mold should be. α for ABS plastic α= 53.0x106/C°, for steel α=...
  18. H

    How Does Thermal Expansion Affect Stress in a Bar?

    Hi, I have been asked to determine the stress in a bar which has a diameter of 50mm when the temperature changes from 20 C to 50C. That's the first part. Secondly, I need to then answer whether or not the stress will be sufficient enough to raise a constraining load of 40 tonnes. Young's...
  19. P

    Thermal conductivity value of (.17-.20)W/m.K

    I was hoping someone could help me with a project I am doing. I have contacted a manufacturing company thatmakes thermal wrap material, and I need to see if this will work for my project. According to the manufacturer the material is 1/16" thick - this info was also given to me by the...
  20. F

    Density change due to thermal linear expansion

    Homework Statement A certain metal has a coefficient of linear expansion of 2.00 × 10-5 K-1. It has been kept in a laboratory oven at 325°C for a long time. It is now removed from the oven and placed in a freezer at -145°C. After it has reached freezer temperature, the percent change in its...
  21. C

    Does an object lose thermal energy due to gravity alone

    If I have an object say a 1kg lump of metal. it is at a temperature of say 20c. I then take that object and raise it and place it on a shelf, does it lose any thermal energy due to the new height, In other words does it cool down for no other reason than being raised to a different elevation...
  22. C

    Thermal Energy Transfer: A Gas Heated at Constant Volume and Pressure

    A quartz tube contains one mom of gAs at 20 deg c. The gas is heated at constant volume to 300 deg c. How much thermal energy is transferred to the gas? If the same amount were heated at constant pressure, how muh energy would be required? I know how to solve this for constant volume using E=...
  23. N

    Thermal Expansion of Brass piston in Steel cylinder

    Homework Statement You have been assigned to design brass pistons to slide inside steel cylinders. The engines in which these pistons will be used will operate between 20.0 degrees Celsius and 150.0 degrees Celsius. Assume that the coefficients of expansion are constant over this temperature...
  24. F

    Thermal Properties - Energy and velocity of molecules

    Thermal Properties -- Energy and velocity of molecules Hello all, Homework Statement (a) Calculate the total rotational kinetic energy of the molecules in 1.00 mol of a diatomic gas at 300K. (b) Calculate the moment of inertia of an oxygen molecule. Treat the molecule as two massive...
  25. R

    Gap between the plates of a Thermal Electric Modules

    Dear Experts Does anyone know how big can we extend the gap between the 2 plates? Thanks. Regards Ramone
  26. S

    Thermal Physics and Bottle Shake

    Homework Statement If you were to shake bottle with some water in it for about ten minutes, then roughly, how much would the temperature increase? Homework Equations K=1/2mv^2 U=N*f*1/2*k*T The Attempt at a Solution I think we need to find kinetic energy and assume it all gets...
  27. L

    Calorimetry: Thermal energy going into translational KE

    Homework Statement Suppose a cup of boiling water (m=250g) instantaneously cools to room temperature (25°C) with the liberated thermal energy going into translational KE. How fast will the cup fly off the table? Assume the water molecules have 18 degrees of freedom. Homework Equations...
  28. J

    Linear Potential and Thermal Equilibrium

    "Linear" Potential and Thermal Equilibrium Homework Statement Consider a classical particle moving back and forth along the x-axis while restrained by a "Linear" potential V(x) = b|x|. If the particle is in thermal equilibrium with the environment at temperature T, calculate the mean value...
  29. S

    How Is Heat Flow Calculated in a Constant Temperature Quasistatic Process?

    Okay, so firstly sorry if this is a poor post/wrong topic, I'm kind of new here, and it's been a while! I'm given an example of a quasistatic process, in a frictionless piston. The piston compresses an ideal gas from Vi to Vf, and pressure increases from Pi to Pf, all at a constant temperature...
  30. C

    Does steam rising in an insulated tube lose thermal energy

    I want to propose an interesting thought experiment, but don't want to A/ make a bigger fool of myself than I normally do B/ well that's about it really The premise behind my experiment is that rising steam does not lose thermal energy if we ignore thermal losses both radiative and conductive...
  31. B

    Thermal Simulation Software (Flixo vs Therm)

    Hey All, Have any of you ever worked with thermal software such as Flixo and Therm? I'm having a problem with U-Value calculations differing between the two programs, and I would really liek to get to the bottom of why. What I'm thinking: I am coming up with some ideas based on some...
  32. P

    Thermal expansion of an interference fit

    I have a bearing that is fixed into its housing by means of an interference fit (to test the effects of having a bearing that has become stuck due to build up of contaminants). I am using a bearing of ID 15.92mm ± 0.005 made of High lead Tin Bronze Alloy with a thermal coefficient of expansion...
  33. S

    Thermal Expansion Aluminium Problem

    A brass ring of diameter 10.00 cm at 19.9°C is heated and slipped over an aluminum rod of diameter 10.01 cm at 19.9°C. Assume the average coefficients of linear expansion are constant. (a) To what temperature must the combination be cooled to separate the two metals? Brass=19 x 10^-6...
  34. M

    Thermal radiation question. Please help me explain the theory

    Thermal radiation question. Please help me explain the theory! I want to delete this post.
  35. F

    Finding thermal equilibrium of hot iron placed in water

    Homework Statement You cool a 100g slug of red-hot iron (temperature 745 degrees C) by dropping it into an insulated cup of negligible mass containing 85g of water at 20 degrees C. Assuming no heat exchange with the surroundings, what is the final temperature of the water? Homework...
  36. L

    Thermal Vent Communities In Antarctica

    Apparently, British researchers have discovered thermal vent ecosystems in the Antarctic Ocean. Of particular interest (to me, at least) was the discrepancy of species found around these events vs. thermal vents in all the other oceans of the world. There has always been some mystery as to...
  37. F

    How Is Temperature Calculated in a Heated Copper Block?

    Hi, Suppose a copper block is heated on one side so that one end is at 800K. Given the dimensions of the copper block, is there a way of calculating the temperature of a point in the block distance x from the heated end after a given time? With many thanks, Froskoy.
  38. Z

    What is the correct method for solving thermal conductivity in this problem?

    Homework Statement One end of a metal rod is maintained at 100 degrees C, and the other end is maintained at 0 degrees C by an ice-water mixture. The rod is 60 cm long and has a cross-sectional area of 1.25 cm^2. The heat conducted by the rod melts 8.50 g of ice in 10.0 min. Find the thermal...
  39. C

    Thermal Superconductor Design: Possible?

    Go easy on me, as I have no formal condensed matter education and just the highest undergraduate quantum physics and chemistry offered at my university. I read a lot of papers and did extra studying while taking those classes, but I'm definitely rusty on the mathematics. Feel free to give me...
  40. C

    Thermal expansion of tank and contents.

    Homework Statement At 5°c, a steel tank is 6m high, 9m in diameter, and contains oil to the 5.9m level. A heating coil is put into service, causing 3.4m^3 of oil to spill over the top of the tank by the time the final temperature is reached. Calculate the final temperature, if the coefficient...
  41. B

    Thermal Energy vs Heat: Understand the Difference

    According to my textbook... Thermal energy is the kinetic energy of the component particles of an object and is measured in joules. Heat is the thermal energy that is absorbed, given up or transferred from one object to another. But later on the book there is a small chapter called...
  42. R

    Is thermal transpiration a real thing?

    I have a video on youtube about a crooke's radiometer, and one of the comments referred to a line from wikipedia about thermal transpiration: I also found a thread about this very subject several years back, but the one link I was interested in (a paper in arxiv) was outdated, and I couldn't...
  43. L

    I from a physics brain: thermal capacity, conduction, cooling

    I am doing a zainy experiment at home. I need to devise a way of applying a cooling intensity factor (CIF) of around 70 mW/cm2. I need to cool material that is roughly 30 degrees Celsius down to around 2 degrees Celsius. The cooling has to last for a period of one hour or more. The surface...
  44. V

    Thermal condution? little confusing can u to remove my doubt.

    thermal condution? little confusing can u please help to remove my doubt. According to law of thermal conduction dQ/dt=-kAdθ/x. variable have their usual meaning. first of all i want to know what is meaning of dQ/dt in this law?? If we see it in a cylindrical object with it's curved part...
  45. N

    Thermal Storage Simulation in TRNSYS Software

    Hi all, As part of my Final Year Project I am studying the feasibility of domestic seasonal thermal storage in water tanks. I am hoping to model this system and have been looking at the TRNSYS software for doing so. I know that this is possible to do because I have seen a number of studies in...
  46. R

    Steel Building Height Variation in Summer vs Winter: Thermal Physics Analysis

    Thermal Physics (Help me!) Following an engineering design, a building is constructed using a steel framework that is 50m high. How much taller is it on a summer day when the temperature is 38oC than on a -5oC winter day?
  47. D

    Passive mechanical safety: thermal sense rods.

    So, I had this idea for passive safety. Break-apart rods (zirconium with low-melting point metal inserts for example) which go through reactor core at regular intervals, are tensioned by springs, and in the event of overheating, are torn apart, operating simple (springs, latches) mechanisms to...
  48. T

    Solid mechanics thermal stress of infinite cylinder

    Homework Statement My problem is to calculate the Thermal stress of a Cylindric shell with inner radius a and outer radius b the inner surface is experiencing Temperature T1 and the outer surface is experiencing T2 with T1>T2 assuming that the linear thermal expansion coefficient is a, the...
  49. D

    What is the Relationship Between Coefficients for Thermal Expansion?

    Hi Physicsforums, I was trying to derive the formula that the coefficient for volume expansion, β, is 3 times the coefficient for length expansion, \alpha. As a reminder, the formulas are: \DeltaL = \alphaLo\DeltaT and \DeltaV = \betaVo\DeltaT where, supposedly, \beta = 3\alpha...
  50. Telemachus

    Why Is Thermal Radiation Usually Negligible in Solids?

    Hi there. Here is the deal. In my lab work, I've done experiments concerning on heat conduction. Now my professor had corrected my inform, and asked me a question for which I have no answer. I consulted for my work the book "heat conduction in solids" by H.S. Carslaw. The book says at the...
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