Thermal Definition and 1000 Threads

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. B

    Thermal Equilibrium: Exchange of Kinetic Energy

    as we know that atomic collisions are perfectly ellastic perfectly ellastic collisions are given by v1=u1(m1-m2)+2(m2)u2 / m1+m2 and v2=u2(m2-m1)+2(m1)u1 / m1+m2 when m1=m2 v1=u2 v2=u1 we know heat is stored in the form of vibrational energy(kinetic energy) so to exchange energy...
  2. S

    Differences between heat capacity and thermal conductivity/convection

    Homework Statement I learned that the heat capacity is the amount of energy absorbed to raise the temperature of a body by 1 degrees. While conduction is the process of heat transfer by vibrations. That being said, when I supply 1000N of heat to 2 rods of different material but same mass the...
  3. K

    Average thermal conductivity (?)

    Hey all, i'm trying to set up a thermal model of a permanent magnet synchronous electric motor. This by doing a lumped system analysis of the motor. In the thermal network that I've set up, I'm trying to introduce an equivalent thermal conductivity value (W/mK) for the copper conductors plus...
  4. E

    Origin of thermal radiation in humans.

    hi, i m new to this forum,this is my first post,i have recently started studying heat transfer. i m am little bit confused about the origin of thermal radiation in human beings.i mean radiations are emitted when an electron jump from a shell/orbit which is far from the nucleus to a shell which...
  5. DaTario

    Light scattering and thermal emission of a body

    hi All, We know from QM that black bodies at temperature T emits light in a well stabilished patern. Now what if the body has color? Which is the emission patern of a green snooker ball for example, at temperature T? When scattering white light we see this ball green because it absorbs...
  6. S

    A Simple Model of Thermal Transfer in Air

    I'm making a Minecraft mod, and I need a bit of help. Quite simply, it simulates heat transfer. Unfortunately, I don't know enough about the subject to construct a good model. Here's what I have so far: Looking back, I can see that simulating heat in terms of watts is probably a really silly...
  7. A

    An Introduction to Thermal Physics by Schroder - any thoughts

    Hi! I'll be covering the above book next semester and was wondering if there is anything I should be particularly aware of about thermal physics. -aLearner
  8. P

    What happens to the temperature of an object in vacuum?

    Hi guys. I was wondering, what happens to the temperature of a object if it's put into vacuum? Say you have a box of steal (something that transfers thermal energy fast between the inside and outside). Inside the box you have a rock. The rock is held in the center of the box using...
  9. P

    How to Calculate Thermal Expansion in a Rod of Length 'l'?

    Consider a rod of length 'l'. When heated, its temperature got increased by 't'. Increase in its length = l\alphat. total length be (l1) = l + l\alphat. Again the rod is heated and the temperature further got increased by 't'. Total length be l2. l2 can be calculated in two ways, l2 = l1 +...
  10. O

    Heat rate flow through bar? and thermal conductivity

    Homework Statement A hot reservoir is maintained at a temperature of 78 oC, and a cold reservoir is maintained at a temperature of 5oC. They are separated by 11.00 cm, and are connected by a cylindrical bar made of two materials. The radius of the bar is 0.83 cm. The upper part of the bar is...
  11. T

    Proving a thermal conductivity/resistance formula.

    Homework Statement The figure below shows a block that consists of two materials with different thicknesses l 1 and l 2 and different thermal conductivities λ1 and λ2. The temperatures of the outer surfaces of the block are Thigh and Tlow, as shown in the figure. Each face of the block has a...
  12. C

    Problem Relating Temperature and Thermal Energy

    Homework Statement An ideal gas is at 40°C. The gas is cooled, reducing the thermal energy by 35%. What is the new temperature in °C?Homework Equations I'm not sure there is one? The Attempt at a Solution Since, in an ideal gas, thermal energy is proportional to temperature, I multiplied 40°C...
  13. B

    Thermal Energy problem - Ice placed in water

    Homework Statement An ice cube at its freezing point is placed in nested Styrofoam cups which contain 240g of water at 21.5 degrees C. If the final equilibrium temperature when the last trace of ice melts is 15 degrees C, what was the mass of the ice cube? Homework Equations mCΔt = -mCΔt...
  14. H

    Thermal Physics: Ice skating temperatures

    Homework Statement It is said that good ice skating only occurs when the ice below the skates melts. Using the Clausius-Clapeyron equation, estimate the coldest temperature at which good ice skating can occur. (Water expands 9% on freezing, Latent heat of ice melting is 334 kJ/Kg, the contact...
  15. T

    Calculating thermal energy released when aluminum cools an solidifies

    Homework Statement While forming a 1.5kg aluminum statue, a metal smith heats the aluminum to 2700 degrees C, pours it into a mould, and then cools it to a room temperature of 23.0 degrees C. Calculate the thermal energy released by the aluminum during the process. Homework Equations Q =...
  16. H

    Thermal Physics- Can you make good tea at a certain temperature

    Homework Statement According to experts good tea can only be made at temperatures greater than 96 degrees celsius. If this is true, can you brew good tea at elevation 4.5km (Pressure = 6.2*10^{4}Pa) . Given that latent heat of vaporisation for water is 2.4*10^{6} J/kg and water has a molar...
  17. H

    Thermal physics- Can you make good tea at a certain pressure?

    Thermal physics- Can you make good tea at a certain pressure!? Homework Statement According to experts good tea can only be made at temperatures greater than 97 degrees celsius. If this is true, can you brew good tea at elevation 4km (Pressure = 6.2*10^{4}Pa) . Given that latent heat of...
  18. S

    Thermal Insulation Of Hydraulic Cylinders

    Hi All, I'm working on a Hydraulic Tire Curing Press Project.There are Hydraulic cylinders in many regions of the press.Steam @ 220 deg c is used to heat the tire to bring about vulcanization process.The press earlier supplied to the customer had thermal insulation problems due to which the...
  19. C

    Thermal expansion coefficient of a Debye solid

    Homework Statement A solid's thermal expansion coefficient is defined as δ= \left(\frac{1}{V}\frac{∂V}{∂T}\right) In the Debye model and at the low-temperature limit, show that δ is a positive quantity and is proportional to T^{3}. At the high-temperature limit, show that δ is still...
  20. L

    How to Estimate Phonon Properties in a Crystal at Low Temperatures?

    Homework Statement a) estimate the number of phonons in a 1mm cube of a crystal at 10K, taking a sound speed of 1000m/s. b) estimate the frequency ω for which you will find the highest phonon nrg content in the range of ω to ω+dω. (Again, assume low temps). Give your solution in the form...
  21. H

    Influence of thermal expansion on thermal conductivity

    Hi everyone. I was wondering if there is a convention for solving heat conduction problems. Specifically should one account for thermal expansion? The SI units for thermal conductivity are W/m/K. Does m include thermal strains already? It seems for basic problems it would be easier to...
  22. S

    What Makes Aluminium an Effective Thermal Radiation Shield?

    Hi all I'm doing a project for energy efficient buildings with thermal insulation.(Just a leisure project and I am not technically that strong!) This is about thermal radiation shielding. My understanding is that Aluminium has higher reflectivity (Hence lower emissivity ) so that it...
  23. J

    Computing Jupiter's Thermal Time Scale

    1. Jupiter radiates more energy than it receives from the Sun by 8.7x10-10L0. Jupiter's radius is 7.0x109cm and its mass is 1.9x1030g. Compute its thermal time scale. Could gravitational collapse power this luminosity for Jupiter's entire lifetime of 4.5 Gyr? 2. Kelvin-Helmholtz (aka...
  24. S

    What is Maxwell Distribution, Thermal Equilibrium, Fluctuation and Wein's law?

    I was reading a book, 'Introducing Quantum Theory' by J.P.McEvoy, and I find it difficult to understand in details of Maxwell Distribution, Thermal Equilibrium, Fluctuation, Wein's law and Planck's quantum theory, so I am finding it difficult to follow Einstein's explanation of photoelectric...
  25. S

    A thermal physics question about steam and coffee, please could you help?

    Homework Statement A coffee machine in a café passes steam at 100°C into 0.18kg of cold coffee (s.h.c. the same as that of water(4200j/kg/K)) to warm it. If the initial temperature of the coffee is 14°C, what mass of steam must be supplied to raise the temperature of the coffee to 85°C Homework...
  26. A

    Thermal conduction of heat by a solid body

    Hello.. The query is regarding thermal conduction of heat from a solid body: Suppose we have a long metallic rod which is insulated on the curved surface and one of the bases. If we supply Q amount of Heat for a small time to the rod from the non-insulated end, initially the temperature of...
  27. S

    Analytical solution for thermal stresses in a rectangular plate

    Hello everybody, I am solving a 2D problem of thermal stresses in a rectangular plate in which temperature is changing only y direction. Plate has fixed displacement conditions. Could anyone help me to find out analytical solution of thermal stresses for my problem? Does anyone suggest me...
  28. M

    Gas heated under constant pressure - thermal energy transferred?

    Homework Statement A 1.0 sample of nitrogen gas (diatomic)is heated at constant pressure from 300K to 420K, Cp (nitrogen) = 29.1 Jmol-1°C-1 The thermal energy transferred to the gas is? 1. 8370 J 2. 12,200 J 3. 34.90 J 4. 3590 J 5. 12.20 J Homework Equations KE = 1/2mv2 =...
  29. O

    Calculating Thermal Radiation: Power and Wavelength of a 47000K Object

    Consider a 47000K object that emits thermal radiation. How much power does it emit per square meter? What is its wavelength of peak intensity?What formula do I use to solve these questions?
  30. S

    Effect of Prandtl Number on Thermal Boundary Layer

    I'm currently having a bit of an intuitive problem understanding the Prandtl number effect on boundary layers and I'm hoping that someone can explain it better than what I've read in some heat transfer books. According to various HT books, a low Prandtl number means that heat diffuses quickly...
  31. T

    Writing Nodal Equations for a Thermal System

    So I have to write out nodal equations for a system that I was given, and I started off by drawing out the flow diagram to see where everything was. I'm having trouble starting the nodal equations though. The attachment has 2 diagrams: figure 1 is the correct diagram that models the thermal...
  32. P

    Find temperature rise of Cylinder from Linear Thermal Coefficients

    Homework Statement Part 1: I have a cylinder of radius R and lengh L. At first i can assume that we have expansion in both R and L. And that i can use the linear thermal expansion coefficient(\alpha) = 4 \times 10^{-6}. The relative change in R and L is 1 \times 10^{-4}, and from that i have...
  33. H

    Extracting thermal neutron cross-sections from ENDF libraries?

    Hi Everyone, Does anyone know of a tool that can extract thermal neutron cross-section data from endf for all availible isotopes? I'm trying to help my professor compile some data to modernize one of his courses. I'm trying to find a list of capture and scattering cross-sections for a wide...
  34. B

    Thermal Physics Introduction- solving for entropy and temperature change

    Homework Statement A container is divided into two parts by a thermally conducting wall. There are N atoms of a monatomic ideal gas on the left side, 2N on the right. The gas on the left is initially at absolute temperature 200K, the gas on the right at 500K. a. After thermal equilibrium...
  35. V

    Calculating Area of Thermal Expansion for Non-Isotropic Materials

    Homework Statement A non-isotropic material is heated, fractional increase in length is different along different directions. With length l1=6.1 cm and l2=6.0 cm. In direction of l1, the coefficient expansion is \alpha1= 10×10-5 K-1 and direction l2 is \alpha2= 40×10-5K-1. The plate is heated...
  36. P

    Thermal expansion (and the Michelson Morley experiment)

    Homework Statement (B) http://imgur.com/VL4aG although I showed the rest of the problem for context if needed Homework Equations ΔL=αLΔT The Attempt at a Solution I'm a little confused by the wording of the problem. When we find the shift in ΔN, are we actually finding Δ(ΔN)...
  37. C

    Positioning Device Based On Thermal Expansion

    Homework Statement In an experiment, a small radioactive source must be moved at extremely slow speeds. A positioning device based on thermal expansion was devised where the radioactive source is attached to one end of an aluminum rod and a heating coil is wrapped around a selection of the rod...
  38. N

    Transforming kinetic energy into thermal energy

    Homework Statement Two cars collide head on while each is traveling at 80 km/h. Suppose all their kinetic energy is transformed into the thermal energy of the wrecks. What is the temperature increase of each car? You can assume that each car's specific heat is that of iron. Homework Equations...
  39. T

    Transistor output resistance and thermal voltage

    A couple questions: I'm in the process of making some small amplifiers and using bjt's in the small signal realm. I have used bjt's as switches for quite a while, so I am quite familiar with their basic operation. I was reviewing small signal analysis trying to refresh my memory about how...
  40. G

    Zero-point energy + Thermal runaway

    IF I am in error, forgive me. but I had this thought cross my mind today. IF absolute 0 is the stopping of all atomic (or molecular) movement. and you induce a thermal reaction, i.e. splitting the nuclei. would the reaction be slowed down at all? (to make a slow burn) Yea. I understand...
  41. A

    Thermal: taylor series van der waals equation

    Homework Statement Show that at constant volume V and temperature T but decreasing number N=n*N_{A} of particles the Van der Waals equation of state approaches the equation of state of an ideal gas. Hint: Rearrange the equation of state into the explicit functional form P=P(v,T) and use x=1/v...
  42. X

    Thermal Conductance Through Two Materials

    I had a thermal conductance homework problem where heat flowed through gold, and then silver. Both materials were of the same length and same cross sectional area. The problem mentioned that the energy transfer had reached a steady state, and I found through doing the problem that under these...
  43. T

    Probability Problem 1.15 From Statistical and Thermal Physics, Reif

    Homework Statement A set of telephone lines is to be installed so as to connect town A to town B. The town A has 2000 telephones. If each of the telephone users of A were to be guaranteed instant access to make calls to B, 2000 telephone lines would be needed. This would be rather extravagant...
  44. T

    Probablity Problem 1.3 From Statistical and Thermal Physics, Reif

    Homework Statement A number is chosen at random between 0 and 1. What is the probability that exactly 5 of its first 10 decimal places consists of digits less than 5?Homework Equations Binomial Coefficient = \displaystyle \binom{N}{n1} Where n1 denotes "n1" objects of an indistinguishable type...
  45. M

    Calculate Thermal Resitance from Heat Sink Geometry

    Hi all, I have a heat sink for which I know the exact geometry (have the CAD model). This heat sink was custom designed and machined from a hunk of aluminum, though it is very basic and I have a hunch I can find an extrusion or OTS part that will match its performance. Rather than trying to...
  46. J

    A question about position of piston after achieving thermal equilibrium

    A vertical cylindrical container contains some helium gas that is in thermodynamic equilibrium with the surroundings. The gas is confined by a movable heavy piston. the piston is slowly elevated a distance H from its equilibrium position and then kept in the elevated position long enough for the...
  47. Q

    Exploring the Role of Thermal Convection in Refrigerator Cooling Systems

    in refrigerators, why cooling boxes are kept at top?
  48. Q

    Understanding Winter Thermal Conduction on Wooden Floors

    in winter, wooden floor feels cold to the barefoot but the rugs and carpets don not feel cold although the floor and carpet are at the same temperature?
  49. H

    Thermal Equilibrium between a Hot and Cold Body

    Just a quick question relating to thermal equilibrium between a hot and cold body. If a hot body and cold (closed systems) are opened up to each other, the thermal energy will be transfer from the hot body to cold body through conduction. So even when thermal equilibrium is reached, the...
  50. A

    Thermal expansion, cup overflowing?

    Homework Statement Coefficient for thermal expansion for glass is β1 = 25x10^-6 K^-1 Coefficient for thermal expansion for this particular liquid is β2 = 300x10^-6 K^-1 The glass cup is completely filled with the liquid at 4.0 L. The temperature of the glass and liquid both increased by...
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