What is Thermal physics: Definition and 198 Discussions

Thermal physics is the combined study of thermodynamics, statistical mechanics, and kinetic theory of gases. This umbrella-subject is typically designed for physics students and functions to provide a general introduction to each of three core heat-related subjects. Other authors, however, define thermal physics loosely as a summation of only thermodynamics and statistical mechanics.
Thermal physics can be seen as the study of system with larger number of atom, it unites thermodynamics to statistical mechanics.

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1. B Thermal physics, COP upper bound for heat driven heat pumps

I made a presentation where I derived, or at least attempted to derive, the formulae for the upper bounds of the efficiency/cop (cop = coefficient of performance) for a heat engine, work driven heat pump, and a heat driven heat pump with 3 thermal reservoirs, hot, warm, and cold. There are many...
2. Maxwell-Boltzmann Distribution

1. ##\vec{p}=m\vec{v}## ##H=\frac{\vec{p}^2}{2m}+V=\frac{1}{2}m\vec{v}^2## ##z=\frac{1}{(2\pi \hbar)^3}\int d^3\vec{q}d^3\vec{p}e^{-\beta H(\vec{p},\vec{q})}## ##z=\frac{Vm^3}{(2\pi \hbar)^3}\int d^3 \vec{v}e^{-\beta \frac{mv^2}{2}}## ##z=\frac{Vm^3}{(2\pi \frac{h}{2\pi})^3}\int d^3...
3. I Surface Absorptance Without Radiant Emittance

how can I go about finding the surface absorptance of a material if I'm not given the radiant emittance of the non- black body?
4. Thermal physics question: Specific heat capacity

At first, I tried to calculate the heat energy required by doing this: I realized I should calculate heat energy separately instead of grouping glass and water together so I did this: But the answer is supposed to be 6.29 x 10^4. I don't know how to solve this. Can anyone help please? Thank you
5. Thermal Physics Problem -- Dropping a hot mass of iron into 20C water

Hi, The solution for this question is thermal energy lost= thermal energy gained 0.200x450x(300-T)=1.0x4200x(T-20) T=26 degrees celcius. However, I am struggling to grasp why (300-T) is used. I have always known a change in something to be final - initial. Therefore change in T= Final-...
6. Entropy Change & Heat Transferred to a Gas

By using the given relationship that S=a/T --(1) along with the equation ∫ (delta Q rev)/T=∫dS -- (2) I found out that my answer for the value of Q is mc*ln (T2/T1)*a upon equating (1) & (2). But the solution is instead given as Q=a*ln*(T1/T2). I would be grateful if someone would point out...
7. Question on RMS Mean Free Path

lambda (rms)= v(rms) * t(rms) -- 1 Now I assume here that t(rms)=1/(√2*n*π*d^2*v(rms)) But this cancels the v(rms) term when used in eq (1) so the mean free path and the RMS free path would actually be the same (even later on when used in the aforementioned Survival Equation) I would like to...
8. To find total work done from multiple reversible processes

The question is given in 3 parts. For first part, process is isochoric so Work done=0. We know here that at end of the process (a), T2=T1 while V remains constant (we can take it as V1) so P2=2P1. For second part, process is isothermal so T is constant. At end of process we reach P1 again from...
9. Maxwell's Distribution Law (Thermal Physics)

There are two questions in the photo. I have attempted the solution (attached below) and I would be highly obliged if someone would verify the same. Edit- Sorry the images of the solution have uploaded in the wrong order. 5th and 1st Image comprise of both parts of Q1 while the remaining of Q2.
10. Question on First Law of Thermodynamics (Paramagnet)

For the first part, I have expressed it in the following differential form- dU= delta (Q) + BdM Now for the second part I am having major confusion. I know that B corresponds to P and M corresponds to V as generalised force and generalised displacement respectively for a Paramagnetic substance...
11. Mean Free Path (Introductory Thermal Physics)

We have the area of incandescence. Using that we can find the radius and subsequently the diameter. A=π* r^2 -----> r= 0.0025m so d=0.005m Using the formula (given by Clausius as we are not specified in question whether it's a Maxwellian distribution or not) Mean Free Path λ=...
12. Question in Thermal Physics (Van der Waals' Equation)

<Using the hint, I tried to find the van der Waal constants in molar form. Since STP is mentioned, I used the unitary method relationship- 22.4 L=22400cm^3=1 molar V <To find a possible conversion standard between cm^3 and mol; which turned out to be 1cm^3= 4.46*10^-5 mol. <Then I used the...
13. Thermal Physics: Computer cooling

Hello folks, I have a bit of a time sensitive question, if anyone happens to read this soon. A computer box consumes 80W power constantly. Outside temperature T= 290 Kelvin. Ambient pressure 10^5. If all the heat generated is expelled at 5 litres per second, estimate the inside...
14. Calculate the Mass of Ice cubes needed to cool a soft drink

Summary:: TLDR : Drink cooled from 17 C to 7 C with either ice cubes (method 1) or soapstone stones (method 2). Calculate the mass of each item that would be needed to cool the same drink. Given the information provided. In order to cool a drink (“cola” for example) from a storage-room...
15. Gas effusing through hole, working out time dependence

Consider instead a thermally insulated container of volume V with a small hole of area A, containing a gas with molecular mass m. At time t = 0, the density is ##n_0## and temperature is ##T_0##. As gas effuses out through a small hole, both density and temperature inside the container will...
16. Rate of flow - thermal physics

Frankly, i don't even know how to start this. I deducted from the solution, that they must have used power/(specific heat capacity x temperautre), however i don't understand how that will give the rate of flow of air. Could anybody help, please?
17. Thermal physics -- Converting the internal energy of argon atoms to temperature

I tried using U=3/2 NKbT, but i don't seem to get the correct answer..
18. Intro Physics Undergrad Thermal Physics recommendations

Hey guys, I have Thermal as a course in this (undergrad) semester and the teacher is very bad. Any book recommendations for me to study entirely on my own? This is what we have to cover in the course:
19. Thermodynamic equation of differentials (and how to work with them)

Disclaimer: I am not a mathematician, I am a physicist. The thermodynamic identity is usually expressed in the following differential form $$dU = TdS - PdV + \mu dN,$$ where U , T , S , P , V , \mu and N are the internal energy, temperature, entropy, pressure, volume, chemical...
20. Question about thermal physics -- Ice cubes melting in water

First, I calculated the heat required for the ice to melt: Q=mLf Q=0.150×330 Q=49.5 J Then, I calculated the final temperature of the water by forming the following equation: Q=mcΔT −49.5=(0.15+0.35)×4200×(Tf −80) Tf=80.0 degrees Celcius But the answer says 32 degrees Celsius.
21. Thermal physics problem -- Pressure and temperature of air in a refrigerator

There is this one problem from past exam papers which I cannot seem to do: The air in a kitchen has pressure 1.0 x 10^5 Pa and temperature 22'C. A refrigerator of internal volume 0.36 m^3 is installed in the kitchen. (a) With the door open the air in the refrigerator is initially at the same...
22. Resistance of Platinum decreases with an increase in temperature ?

Basic Procedure The experiment basically involves finding the null point on the Carey Foster's bridge with the PRT as the unknown resistance and using a Resistance box as the variable resistance. In the above diagram, P and Q are 2 fixed resistors of equal resistances. For obtaining the first...
23. I What Determines the Maximum Number of Microstates at Equilibrium?

## \Omega(E_1)## is the number of microstates accessible to a system when it has an energy ##E_1## and ##\Omega(E_2)## is the number of microstates accessible to the system when it has an energy ##E_2##. I understand that each microstate has equal probability of being occupied, but could...
24. I Boltzmann Distribution and microstate probabilities

For a canonical ensemble the probability of occupying a certain microstate varies depending on the energy, however I thought that every microstate has an equal chance of being occupied. So what part of the canonical ensemble have I misunderstood?
25. Thermal Physics: Fermi Gas and chemical potential

Hi all, I have an issue trying to understand the following paragraph from Blundell's book. How, exactly, does the definition of ##\mu_0 = E_F## "make sense"? In the sentence after 30.21, it seems to say that the mean energy for a system with ##N## particles differs from that of a system with...
26. 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...
27. Thermal Physics: Reversible processes

Hi all, I have been having some issues trying to show that a reversible expansion of gas does not create new entropy. Assistance is greatly appreciated! So suppose that a gas expands reversibly as shown below at fixed temperature At fixed temperature, internal energy doesn't change so...

44. Question about Maxwell equation in thermal physics

Homework Statement Homework EquationsThe Attempt at a Solution How to do part ii)? I differentiate part i with respect to p (∂H/∂P)T = T (∂S/∂P)T + V ...(1) Then I used the equation given in the question, Applying maxwell equation I got (∂T/∂V)S = -(∂P/∂S)V ...(2) I planned to substitute...
45. C

Thermal physics -- Latent heat melting ice

Homework Statement Question (b) (iii) Homework EquationsThe Attempt at a Solution The energy required to melt the ice is Q1=mL=3*0.025*3.3*10^5=24750J The energy released by water is Q2=mcT=0.33*4200*(22-T) Shall I calculate the energy that the ice needs after it melts into water? i.e...
46. Thermal Physics: Thermodynamic Identity

Homework Statement Homework Equations ##dS = \frac{1}{T} (dU - PdV)## assuming dN = 0 The Attempt at a Solution I have actually managed to solve all 4 parts correctly, except for the fact that I solved Part d) with the Sackur-Tetrode equation rather than the thermodynamic identity. I...
47. I

Calculating Changes in Internal Energy for a Rising Air Parcel

Homework Statement A 1 kg parcel of dry air initially at a temperature of 15 Celsius (288 K) rises from ground level to its equilibrium height, which corresponds to a pressure of 750 hPa. What is the decrease in internal energy?What is the temperature of the air parcel at its equilibrium...
48. I [Stat Phy] What does exhausting the states of a system mean?

I was reading the *Statistical Physics An Introductory Course* by Daniel J.Amit and need some help to understand a certain passage: In an isolated composite system of two paramagnetic system: System a with ##N_a## spins and a magnetic field ##H_a ## System b with ##N_b## spins and a...
49. Reversibility in thermodynamics

Conceptually, why does infinitesimally changing a system allow for a process to be reversible. For example, if we heat a system at temperature T1 to T2 by using a heat reservoir at T2, it is considered irreversible, but if we heat the system with many reservoirs at temperatures T1+dT, T1+2dT...
50. Problem concerning about thermal physics

Homework Statement A metal rod of length length L, linear coefficient of expansion a, is fixed at both ends to the walls. When the temperature is increased byΔT, the rod bends into a circular arc due to thermal expansion. 2 Relevant equations a)Find the radius of curvature R of the rod by...