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

    Zero point energy in thermal noise spectrum?

    This is a question about the proper form for thermal noise from a resistor. This is purely academic for me - I always work in the regime where \hbar \omega << k T so the noise spectrum is simply P \approx kT. When this no longer holds, quantum effects matter of course. Then I have seen...
  2. M

    How can I calculate the cooling time of a steel ball using thermal radiation?

    Homework Statement Hi! I need some help by my phisycs homework at universty. Here is the problem: We have a steel ball, with density of 7800kg/m^3, with speficic heat capacity 460J/kgK. Temperature of the ball is 1700K. How much time does the ball need to cool down to half of it's temperature...
  3. L

    Thermal resistances adding formula

    Homework Statement Prove a rule for adding of Thermal resistances for: A)R1 and R2 in Series B)R1 and R2 in Parallel Homework Equations The Attempt at a Solution According to the book the result should be : A) R = R1 + R2 B) 1/R = 1/R1 + 1/R2 So i thought we can get some ideas from the...
  4. W

    Improving thermal conductivity of RTV silicone for hard candy

    I use RTV silicone rubber to make moulds for hard candy. Hard candy is basically boiled sugar that is poured into moulds at just under 300 degrees F. The castings of hard candy develop bubbles on the surface because the silicone does not dissipate the heat, unlike traditional metal moulds...
  5. A

    Thermal simulation with SolidWorks (looking for tutorials/sources)

    Dear PF-ers (whats a thing right?), Alright as per previous experience, I ask what I'm looking for first, then explain (for those lazy readers): I am looking for some books/ebooks/sources specifically relating to simulation (Thermal) in Solidworks. I've gone through all videos on Youtube and...
  6. E

    Sources of error in thermal expansion

    I was just wondering what would be sources of error in calculating thermal expansion
  7. E

    Thermal Expansion-how much has the ocean expanded

    The ocean’s average temperature has risen by approx 0.375°C over the century. Use this value to estimate by how much the ocean water might have expanded in items of percentage increase. This is what i started doing but I do not think this is right. Coefficient of Cubical Thermal Expansion...
  8. M

    The rate of thermal energy transfer

    Task: A steady flow boiler takes in feed water at 1.5kg/s, at a temperature of 30 °C. The water is heated and turned into wet steam. This leaves at 1.5kg/s, with a pressure of 10 bar and a dryness fraction of 0.97 to the superheater, where it receives heat at a constant pressure and emerges...
  9. Z

    Thermal effect of heat input on an iron rod - magnetostriction

    If an iron rod, inside two coils, incurs current going through the coils in the same direction, then the rod will increase in length and then it will begin to reduce in length. This is due to the magnetostrictive properties of the iron. When the currents oppose each other, so as to cancel...
  10. P

    Thermal analysis and implicit scheme

    why is thermal analysis done in implicit scheme
  11. S

    Rate of thermal conduction in various copper structures

    A cylinder is constructed from a super insulator. The dimensions of the cylinder are Length L: 1 M; inside diameter i.d.: 12 mm. The entire Length of the cylinder contains copper (cases described below). Heat (T > 100C) is continuously applied to the copper on one end of the cylinder...
  12. C

    Common temperature for thermal equilibrium

    Homework Statement One mole of copper at a uniform temp. of 0 Celsius is placed in thermal contact with a second mole of copper which, initially, is at a uniform temperature of 100 Celsius. The pressure in the system is maintained at 1 atm. The two moles of copper are thermally insulated from...
  13. O

    Question related to heat and thermal energy

    Identify the incorrect statemet from the following: A) The thermal energy of an object is the sum total of the kinetic energy of random motions of all its atoms/molecules. B) Heat is the flow of thermal energy. C) Temperature is a measure of the average kinetic energy of random...
  14. R

    Finding work done by downward force and increase in thermal energy

    A worker pushed a 23 kg block 13 m along a level floor at constant speed with a force directed 22° below the horizontal. If the coefficient of kinetic friction between block and floor was 0.40, what were (a) the work done by the worker's force and (b) the increase in thermal energy of the...
  15. S

    Thermal Expansion of a metal ring

    Homework Statement A ring of aluminum has a hole in the middle. When the ring is heated: a) the hole decreases in diameter b) the aluminum expands outward and the hole remains the same size. c) the area of the hole expands by the same percent as the area of the aluminum. d) the area of...
  16. S

    Conversion vs breeding. Thermal and fast reactors.

    Hi there, I have came across a question in past exam papers that basically asks... What do the terms Conversion and breeding mean? I put conversion is the change from a fissionable element to a fissile element such as U238 to Pu239. When more of these fissile products are created than used...
  17. C

    Calculating Total Internal Energy of a System in Thermal Equilibrium

    Homework Statement Consider a system in thermal equilibrium consisting of N particles that have 2 energy states E1 and E2 separated by an energy ΔE. Given that $$N_1 = \frac{N}{exp(-ΔE/k_BT)},\,\,N_2 = \frac{N exp(-ΔE/k_BT)}{1+exp(-ΔE/k_BT)}$$ show that in the case of the lowest energy...
  18. C

    Thermal Stress and Spring Systems

    The rod is made of A-36 steel and has a diameter of 0.25 in and a length of 4 ft. Attached to each end of the rod is a spring which is fixed to a wall. If the springs are compressed 0.5 in. when the temperature of the rod is T=40 F, determine the force in the rod when its temperature is T=160 F...
  19. A

    Science fair - Formula for friction to thermal energy?

    Homework Statement For science fair, I'm doing a project in which we are trying to calculate the force of a thermometer being moved normally, versus a thermometer being slowed down by a high-friction material. The thermometer will (Potentially) read the amount of thermal energy produced by...
  20. J

    Thermal Noise in Electrical Circuits

    Dear people, it might be a simple question, but I have been on this for over 2 days now and can't find a proper explanation of this anywhere: https://dl.dropbox.com/u/2264519/circuit.jpg Picture a RCL circuit which is kept at room temperature. Now even when there is no current going through...
  21. C

    Thermal velocity of particles in the solar corona

    Hello i have a problem with this question if anyone could help me ,that would be great. Estimate the thermal velocity of particles in the solar corona (take a distance two times the radius of the sun and assume that the particules have only two degrees of freedom), thus the thermal energy is...
  22. X

    Book for help in stat and thermal physics

    This is a general question. In struggling hard in my stat and thermal physics course, especially with homework from kittel and kroemer. I am looking for another book that would have more examples so that I can have an easier time with home work problems. Would anyone have any suggestions ?
  23. G

    How Can I Accurately Model Heat Transfer in a Simplified Hydraulic Press Setup?

    Hi all, This is my first post in PF. This is a heat transfer problem.I have started to learn the basics of Heat transfer (I'm in 3rd yr engg).My project coordinator has allocated a problem and I'm having tough time solving it. The Problem statement :(Pl find the attached images) The...
  24. A

    How to calculate thermal exchange rate of Air?

    How would I calculate thermal exchange rate of Air for different amounts of humidity? I'd like to create a graph to show how much radiant heat air would absorb, (at some temperature (10°C) changes depending on the humidity amount, 0 - 100%
  25. U

    The Hydrodynamic and Thermal boundary layers

    Hi, I'm doing 'Heat and Mass transfer' at college and we're covering the topic on the hydrodynamic and thermal boundary layers. I have a couple of questions, the answers to which are not given explicitly in any of my textbooks. 1. During open flow, why does laminar flow eventually have...
  26. heycoa

    Solid State Physics | electrons | thermal conduction

    Homework Statement Explain why electrons carry a net energy but not a net current in the case of thermal conduction. Homework Equations n/a The Attempt at a Solution n/a Please help me understand this!
  27. A

    Maximum thermal cycle range to avoid onset of plasticity

    Homework Statement The linear thermal expansion coefficient of aluminum is 22.2x10-6 m/m K and that of alumina is 5.4x10-6 m/m K. If the criterion for onset of dislocation plasticity is related to thermal mismatch exceeding Burgers vector for aluminum, which is 2.8x10-10 m. What is the...
  28. T

    Understanding Heat and Thermal Energy: Exploring the Relationship and Concept

    Hello all.. I know this thread is asked a lot before and i read some of them.. but to make sure that i understand and to make like a small resume can we say: Heat is the "quantity" of the thermal energy being exchanged? i mean its like the work that is responsible for the change of the kinematic...
  29. A

    Thermal physics final temperature of mixture

    Homework Statement 250.0g of copper at 100.0°C are placed in a cup containing 325.0g of water at 20.0°C. Assume no heat loss to the surroundings. What is the final temperature of the copper and water? Homework Equations Conservation of Energy mcCΔTc = mhCΔTh The Attempt at a...
  30. J

    What is the Mechanism Behind the Emission of Thermal Radiation?

    I'm trying to understand the origin of thermal radiation. All things with a temperature emit electromagnetic radiation. Every discussion I've found starts with that as a premise and then goes on to Wien's displacement law and Planck's law, etc which I follow. But *why* do all things...
  31. R

    Thermal Stress Problem- not sure how to attack this one

    Homework Statement The equation F/A = -Y\alpha\Delta T gives the stress required to keep the length of a rod constant as its temperature changes. Show that if the length is permitted to change by an amount \Delta L when its temperature changes by \Delta T, the stress is equal to F/A = Y(\Delta...
  32. L

    Change in thermal energy and Temperature problem

    Homework Statement Compute the change in internal energy, ΔU, and the final temperature, Tf, when 1 mole of an ideal, diatomic gas is compressed adiabatically to 89.700% of its initial volume. The starting point is 22.500°C and 16.100 L. (Assume that the vibrational degree of freedom stays...
  33. L

    Thermal stress of two peices of metal attacthed to two plates.

    Homework Statement 2)Both, a brass tube and the steel rod located inside the brass tube are solidly attached to common end plates A and B at either end. The respective diameters are : Do = 5.4 [cm] Di = 3.0 [cm] d= 2.8[cm] Brass: alpha=19x10^-6/degree celcius E=210GPa Steel...
  34. J

    Thermal Physics, finding the thermal conductivity of a metal

    Homework Statement One end of a metal rod is maintained at 100°C, and the other end is placed in a large container with ice and water at 0°C. The rod has length 50 cm and a cross-sectional area of 0.8 cm 2 . The heat conducted by the rod melts 4 g of ice in 5 minutes. Calculate the...
  35. E

    Two questions about thermal radiation heat transfer

    Hi guys, could you concretely explain me (also with a simple example) the difference between blackbody emissive power (sometimes found as e'λb) and blackbody radiation intensity (i^{'}_{λb})? and which the difference between a diffuse surface and a surface that follows the Lambert law? Thank...
  36. H

    Calculating Thermal Expansion in a Steel Cable

    Homework Statement As shown in attachment a steel cable is stretched between two poles. In 20°C temperature the cable remains horizontal (the length of the cable 10m). At a higher temperature θ°C the cable bends like in attachment. The lamp hanging from the mid-point could be...
  37. Greg Bernhardt

    Classical Fundamentals of Statistical and Thermal Physics by Frederick Reif

    Author: Frederick Reif Title: Fundamentals of Statistical and Thermal Physics Amazon Link: https://www.amazon.com/dp/1577666127/?tag=pfamazon01-20 Prerequisities: Table of Contents: 1. Introduction to Statistical Methods Random Walk and Binomial Distribution / General Discussion...
  38. L

    Thermal losses through single glazing

    Hello, I have looked through various websites, which show single glazing heat losses (U-factor) to be 5.7 W/m^2.K. But when I use thermal conductivity basic formulas, the yielded results are quite different: k of glass is 1.05 W/m.K; L -> glass thickness is 4 mm = 0.004 m; so: U = k/L =...
  39. S

    Thermal conduction between difference surfaces

    Homework Statement from this video: It showed that a better conductor of heat will transfer heat as well as absorb heat more quickly than a lousy conductor. However, during the transfer the heat is passed from eg metal at 30 degrees to a solid at 20 degrees . So why would the metal being a...
  40. S

    AP PHYSICS ~ Thermal Properties ~ A heat transfer of

    A heat transfer of 9.5 x 10^5 J is required to convert a block if ice at -15°C to water at 15°C. What is the mass of the block of ice? So do I have to use the equation; Q= mcΔT ? and Q= mL ? And if so how do I use it?
  41. S

    What is the final temperature of a lead ball dropped from a height of 4.57 m?

    A 97.6-g lead ball with an initial temperature of 20°C, is dropped from rest from a height of 4.57 m. The collision between the ball and ground is totally inelastic. Assuming all the ball's kinetic energy goes into heating the ball, find its final temperature. PLEASE HELP ME UNDERSTAND THIS...
  42. S

    Thermal Properties of Solids and Gases Problem

    At a local county fair, you watch as blacksmith drops a 0.050-kg iron horseshoe into a bucket containing 25.0 kg of water. If the initial temperature of the horseshoe is 450°C, and the initial temperature of the water is 23°C, what is the equilibrium temperature of the system? Here is...
  43. E

    Thermo Question: The math behind systems in thermal contact

    Hi! I am reading Molecular Driving Forces, 2nd ed., by Dill & Bromberg. On page 53, example 3.9, we consider why energy exchanges between two systems from the point of view of the 2nd law. We consider two separate systems. Each has ten particles, and each particle has two possible energy...
  44. 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...
  45. 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...
  46. 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...
  47. 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...
  48. 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...
  49. 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...
  50. 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
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