What is Thermal energy: Definition and 205 Discussions

The term 'thermal energy' is used differently, and often loosely, in different contexts. It refers to several distinct physical concepts, such as the internal energy, or as the enthalpy, of a body of matter and radiation; or as heat, defined as a type of energy transfer (as is thermodynamic work); or as the characteristic energy of a degree of freedom,




{\displaystyle k_{\mathrm {B} }T}
, in a system that is described in terms of its microscopic particulate constituents, where


{\displaystyle T}
denotes temperature and



{\displaystyle k_{\mathrm {B} }}
denotes the Boltzmann constant.

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  1. A

    B Efficient way to warm a concave body such as Pita bread

    What is the optimal and efficient way to warm a concave body on a plain source of heat (such as heating concave pita bread) on its peak top or opposite (on the larger surface with gap)? Imagine you have a body in U shape. Is the best way to warm it with the U position or opposite?
  2. V

    Therapeutic vs Diagnostic Ultrasound Tissue Temperature

    Hello everyone, I stumble on this forum while searching for reliable explanation of ultrasound thermal energy with regards to temperature increase in superficial human tissue, specifically skin. I have been performing diagnostic ultrasound for almost 30 years, specifically vascular...
  3. lxhull

    Doubling the Thermal Energy of a Frozen Chocolate Bar

    The farthest I got was double thermal energy equals mass times specific heat capacity times change in temperature (115+34) 2Eth=(mc149) To Eth=mc74.5 I'm not sure where to go from here. It seems like I don't have enough information.
  4. lxhull

    Specific Heat Capacity of a metal bar placed into water

    Previously solved thermal energy gained by water as Eth= 0.15(4180)(17.6) = 11035.2 J Not sure if its relevant
  5. mathbrain9

    Link between increase in Potential energy and the thermal energy lost

    "Heat is the transfer of kinetic energy between molecules. If the velocity is more, the kinetic energy will be more so that the heat is more." "As an object's speed increases, the drag force from the fluid increases exponentially. For example, when you drive at high speeds, the frictional force...
  6. P

    How does energy affect the melting point of water?

    Im not really sure how to answer this question. Would you have any ideas?
  7. P

    Is the Calculation of Thermal Energy in Mixing Water and Steam Accurate?

    Q=Qwarm water+Qsteam Q=mct+mLv Q=(8kg)(4200J)(100C-25C)+(2kg)(2.3*10 to the power of 6 J/Kg) Q=7.12*10 to the power of 6 J Is this the correct answer?
  8. S

    Thermal energy dissipated from the brakes in a car

    My sign doesn't check out and I don't get why that'd be the case. Forces that act --> ##F_{fr} and F_g## derivation: ##\Delta K = W_{NC} + W_C (1)## ##\Delta K + \Delta U = W_{NC}## ##\frac 12 mv_2^2 - \frac 12 mv_1^2 + mgy_2 - mgy_1 = W_{NC}## NOTE: ##y_2## assumed to be datum line so ##y_2 ==...
  9. bob012345

    A Rippling Graphene Harvests Thermal Energy?

    It is claimed 2D Graphene sheets can be used to harvest thermal energy while being at the same temperature as the surroundings in seeming contradiction to Feynman's *argument (in the popular accounts). However, the academic papers referenced below make the claim everything is well within known...
  10. B

    Glass Thermal Energy: Solid Glass Beam w/ Spiral Column

    Could I put this on here for answers please ? If produced a solid glass beam with a spiral column thorough the middle of it would the core be hotter or cooler than the surrounding air? If colder could it be use in conjunction with ground source technology to produce hot water? I not sure how to...
  11. Cheesycheese213

    Heating substances in paper cups?

    In class, we briefly discussed those experiments where a paper cup is filled with water and heated, and the cup does not end up burning while the water is able to boil. From what I remember of what was said, although I am not sure I understood correctly, the water has a much higher specific...
  12. A

    Thermal energy/ heat in a parallel connection

    In a parallel connection heat is produced. R1 = 5 Ohm R2 = 10 Ohm What is the relation of W1/W2? 1:4 1:2 2:1 1:8 3:1 I’d tend to say 1:2, but I am not really sure…
  13. Petronius

    Thermal energy question: Final temperature of a solution

    Hello, thank you for taking the time to read this.. I hope I followed the formatting correctly and this post complies with the expectations of the forum. I solved the equation but my answer seems too low. I tried it again and arrived at the same answer. I also had doubts if it was acceptable...
  14. F

    How is absorbed thermal energy invested during a phase change?

    Hello, I was pondering on the well known fact that a certain amount of substance, when absorbing heat, increases in temperature up to a certain temperature and then phase (state) transformation takes place. Any energy supplied at that point does not increase the temperature any further but is...
  15. F

    Why is it more efficient to get thermal energy from a higher temperature source?

    Hello, Internal energy is the sum of the total KE and total PE of the system. Thermal energy is essentially representing the KE of the system and depends on temperature. When studying heat engines, we learn that it is better, in the name of efficiency, to get the same 1000 J of thermal energy...
  16. SebastianRM

    Intro to thermal Physics - D. V. Schroeder -Entropy question

    Hey guys, so I am reading this book and on pages 89-90, the author says: "Increasing temperature correspond to a decreasing slope on Entropy vs Energy graph", then a sample graph is provided, and both in that graph and in the numerical analysis given in page 87 the slope is observed to be an...
  17. DLeuPel

    Does a waterfall have a higher temperature at the bottom ?

    So we have that KE= (2/3)kT , meaning that if I increase the kinetic energy of water, it will become hotter, I searched it and it says that at the bottom of the waterfall, the water is slightly hotter. Of course I imagine that when they refer to the bottom, they refer to a part of the waterfall...
  18. DLeuPel

    Temperature and the kinetic energy of everything

    Earth rotates, it also orbits the Sun, the Sun orbits the galaxies and these have they’re own velocities as well. We know that the kinetic energy is measured by its velocity, and also that kinetic energy is related with temperature. By this I mean that the movement of particles are a measure of...
  19. D

    Thermal Energy when Heating and Cooling a Cabaret

    Homework Statement Having chilled the air until it contains only the perfect amount of moisture, you want to reheat it to the ideal cabaret temperature. You could use an electric space heater or wood fire, but you already have another source of heat: the same system that chilled the air in the...
  20. yecko

    Conduction with thermal energy generation

    Homework Statement I am wrong in my attempt, yet I can't figure out the reason why... Homework Equations (solution with h=250 W/m^2*K instead of 350 W/m^2*K) The Attempt at a Solution This is how I obtain the answers, which I checked all the calculations and I don't think there is...
  21. E

    Internal energy and thermal energy

    I'm watching a lecture introduction internal energy and in it, the lecturer states the following for some system: E_{internal} = E_{translational} + E_{vibrational} + E_{rotational} + E_{other} where ## E_{other} ## could be chemical energy, magnetic energy, electrostatic energy etc. Then...
  22. isukatphysics69

    Where Does Thermal Energy Come From in an Inelastic Collision?

    Homework Statement Homework Equations n/a The Attempt at a Solution I am going through the final exam problem sets right now and just looked at the answer key and wondering where in this system there could be thermal energy? while i was working through the problem i assumed no thermal energy...
  23. mjda

    I Stellar Thermal Energy with no Nuclear source

    Can anyone enlighten me as to why the total thermal energy of a star will increase with time if the star has no nuclear energy source?
  24. K

    Thermal Energy Equation Term - Chain Rule

    Homework Statement I am going through a derivation of the thermal energy equation for a fluid and am stumped on one of the steps. Specifically, the text I am using converts the term: P/ρ*(Dρ/Dt) to: ρ*D/Dt(P/ρ) - DP/Dt where: ρ = density P = pressure D/Dt = material derivative The text...
  25. Jamie_Pi

    Calculate Final volume and temperature of piston

    Homework Statement One cylinder in the diesel engine of a truck has an initial volume of 640 cm3. Air is admitted to the cylinder at 30°C and a pressure of 1.0 atm. The piston rod then does 500 J of work to rapidly compress the air. What are its final temperature and volume? Homework Equations...
  26. F

    Heat engines can organize thermal energy

    Hello, I am reviewing some thermodynamics and heat engines. Heat engines are cyclical machines able to convert a portion (just a portion) of the thermal energy extracted from a hot reservoir into mechanical work. The residual thermal energy must dump into a lower temperature reservoir...
  27. A

    Finding work and the Change in Thermal Energy

    Homework Statement Kerry is pulling a 156-kg sled along a snowy, horizontal path with a 620-N force directed at an angle of 29.0° above the ground. He pulls the sled over a distance of 26.0 m, and the coefficient of kinetic friction between the sled and the ground is 0.0622. I need to find the...
  28. A

    Calculating Work and Change in Thermal Energy

    Homework Statement In the question, a person is pulling a 156 kg sled up a hill. A 620 N force is used to pull the sled up the hill that has an angle of 29° with the horizontal. The sled is pulled a distance of 26 m, and the kinetic friction coefficient is 0.0622. The system has been defined as...
  29. Pushoam

    Mean thermal energy of a system with given potential energy

    Homework Statement Homework EquationsThe Attempt at a Solution ## V(r) = \frac 1{r^3} \left( A - Br^2 \right )## At the bottom of the well, r is verry small. So, ## V(r) = \frac A{r^3}## Assuming the validation of Equipartition of energy theorem, since the degrees of freedom is 1, the...
  30. S

    What differentiates thermal and sound energy?

    Since thermal energy is the vibration of molecules and sound is too, what is the difference? And why exactly do atoms radiate different energies as a result of vibrations?
  31. W

    Problem involving thermal radiation and specific heat

    Homework Statement A satellite to reflect radar is a 3.5-m-diameter, 2.0-mm-thick spherical copper shell. While orbiting the earth, the satellite absorbs sunlight and is warmed to 50 °C. When it passes into the Earth's shadow, the satellite radiates energy to deep space. You can assume a...
  32. Bonapartist

    Thermal energy problem: Gas expansion in cylinder

    Homework Statement A vertical heat-insulated cylinder is divided into two parts by a movable piston of mass m. Initially, the piston is held at rest. The top part is evacuated and the bottom part is filled with 1 mol of monatomic gas at temperature 300 K. After the piston is released and the...
  33. nickyfernandezzz

    Kinetic energy to thermal energy

    Hey guys, I need help with the following question. A lead ball of specific heat capacity 130J/KgK travels with a speed of 100m/s before it hits a wooden cube fixed to floor and gets stuck inside.What will be the rise in temperature of this lead ball by the time it comes to I attempted the...
  34. L

    Finding change in thermal energy Work and Energy problem

    Homework Statement A 26.2 kg child rides a 1.00 kg potato sack down a 2.05 m high slide. If the child starts from rest and has a speed of 1.60 m/s at the bottom of the slide, what is the change in thermal energy of the child on their potato sack and the slide? Homework Equations KE = (1/2)mv2...
  35. Eclair_de_XII

    Finding coefficient of kinetic friction from thermal energy?

    Homework Statement "A rope is used to pull a ##\frac{357}{100}kg## block at constant speed ##\frac{203}{50}m## across a horizontal floor. The force on the block from the rope is ##\frac{768}{100}N## and directed ##15°## above the horizontal. What are (a) the work done by the rope's force, (b)...
  36. Oannes

    Trouble Finding Change in Temp Given KE = Q (Thermal Energy)

    Homework Statement A 3kg projectilce traveling at 100 m/s is stopped by being shot into an insulated tank containg 100kg of water. If the KE of the projectile is completely convereted into thermal energy, how much will the temp of the water increase in degrees celcius? The standard heat of...
  37. Conservation

    Total thermal energy from heat equation

    Homework Statement Homework Equations Heat equation The Attempt at a Solution I can derive E(t) to get integral of du/dt over 0 to L, which is the same as integrating the right hand side of the original equation (d2u/dx2+sin(5t); while this allows me to take care of the d2u/dx2, I don't know...
  38. timallard

    Atlantic Inflow to the Arctic Basin via Pacific Inflow

    [screenshot nullschool ocean-currents-ssta] Inflow from the Pacifc the main flow show drifting east and a general value 0.8-0.9 sverdrup containing 10-Tw/winter, 20-Tw/summer heat-flux of less dense water from freshwater runoff creating a head-height of 40-50cm helping to melt sea-ice from...
  39. J

    How much perspiration must vaporize per hour to dissipate extra energy

    Homework Statement During the game, the metabolism of basketball players often increases by as much as 30.0 W. How much perspiration must a player vaporize per hour to dissipate this extra thermal energy? Assume that perspiration is simply pure water and that perspiration starts at temperature...
  40. Elena14

    I Hot liquid mixed with a cold liquid

    My textbook says - When a hot liquid is mixed with a cold liquid, the temperature of the mixture - "is undefined for some time and then becomes nearly constant". Shouldn't the temperature first decrease and then become constant ? Why does it say "undefined" ?
  41. A

    Exploring Thermal Effects: What Makes Particles Vibrate?

    I've recently begun studying thermal effects. I learned that thermal energy could be transferred within an object through conduction and from a distant object through radiation. (let me know if I'm wrong here) I also learned that when matter is heated, it's particles begin to vibrate, move apart...
  42. JoAstro

    What's the thermal energy of a helium atom?

    I have this formula "E= 1/2 mv^2" which I don't fully understand. Also, I don't have the values for helium's mass and velocity.
  43. N

    Calculating Fire Temperature from Thermal Energy

    is there a way to calculate the themperture of something like a fire, if you know the thermal energy it produces.
  44. Andrei316

    (0.04)c(33.7-23.5)+(0.08)c(33.7-39.6) Find C

    Sorry if the title is against the rules or anything, I just wanted to be specific as possible :P 1. Homework Statement V1(Saltwater) = 40g = 0.04kg V2(Hot-Saltwater) = 80g = 0.08kg Ti(Saltwater) = 23.5oc Ti(Hot-Saltwater) = 39.6oc Tf = 33.7c Question: A cup of 40g saltwater is at 23.5c & A...
  45. B

    Reaction rates, temperature, and thermal energy

    Homework Statement Hi there. My question is more for clarification than a homework question. In my studies, I noticed that my MCAT study manual provides problems relating reaction rates and the effect that temperature and thermal energy have on a reaction. For example, a question asks: in an...
  46. B

    Space Shuttle, thermal energy transfer, book makes no sense

    Homework Statement Space shuttle enters the atmosphere. (i) What happens to the transferred energy? (ii) how do the high temperatures generated in the shuttle enters the Earth atmosphere relate to the material used for the underside of the shuttle surface? Why is the underside not made from...
  47. I

    Thermal energy distribution of an object?

    Hey all, I just wanted confirmation. The thermal energy distribution of molecules in a system corresponds directly to its blackbody curve right?
  48. 3

    Conversion of Thermal Energy into Work

    This question appeared in my IB Physics HL mock exam and I am stumped by the answer on the mark sheet. It really should be a trivial question but it's open to interpretation which is why I find it unreasonable. It was in Paper 1 from November 2014, 1. Homework Statement ? Which of the following...