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1. ### Entropy change is intrinsically positive

How can I prove that the entropy change is intrinsically positive? Given two systems with both of the heat capacities are independent of temperature.
2. ### Isothermal Compressibility of Photon Gas

I am really stuck at this question. I tried to get the equation of volume with independent variables P and T, but the equation itself does not give a nice form, and thus I cannot get the derivative of V with respect to P. What should I do?
3. ### Time-Reversal Symmetry

I completely have no idea what time-reversal mean. Why does, by substituting -t into an equation and if the result is the same as the original equation, then the equation is said to be time-reversal symmetry? Also, what does that 'symmetry' mean there? An even function?
4. ### Internal energy's lower bound

Thermodynamics question: Why does the internal energy have a lower bound? I tried to explain it using postulates, but cannot get the connection between the postulates. Please do explain it briefly. Thank you.
5. ### Dirac notation Schwarz Inequality Proof

Hmm.. I don't get why the proof starts with that |Z> Mind to explain it, please? thanks :)
6. ### Coulomb's Law of Electric Displacement -- Why is there none?

Why is there no Coulomb's Law for the electric displacement?
7. ### Curl of electric displacement

In what condition(s) curl of electric displacement is zero? Is it okay to say curl of electric displacement is zero in: 1) in electrostatics (curl of E is zero) then followed by the following conditions: 2) when there is no polarization (curl of P is zero) 3) in uniform polarization (which...
8. ### Line integral of sphere

What's the line integral of sphere? Is it possible to get the line integral in three dimensions? What kind of line are we integrating?
9. ### Work done by magnetic field

No, I haven't learned that theorem yet.
10. ### Work done by magnetic field

if you pull a loop of wire (to the right) with velocity v and charge is moving perpendicular to your motion (upright) with velocity u, so which velocity does the magnetic force refer to? the loop of wire is immersed in an uniform magnetic field (toward the page)
11. ### Work done by magnetic field

Why magnetic field never do work?
12. ### Magnetic Vector Potential

Not a homework question! I am doing exercises for upcoming final exam. So, I get stuck at question 5.27 (Griffith 4th edition textbook). Question: Find the vector potential above and below an infinite uniform surface current with constant current sheet, K flowing at positive x direction. I...
13. ### Surface bound charge and Body bound charge

What exactly are surface bound charge and body bound charge? Is there any difference between: 1) surface bound charge and surface charge 2) body bound charge and body charge How do we know if surface and body bound charge exist? Does polarized material always have surface and/or body bound...
14. ### Slater Determinant

thank you. I have found out a really easy way to construct Slater determinant for electron spin of an atom :D
15. ### Slater Determinant

thank you! I have another question. Prof taught us one row represents one electron, so each electron is represented in a row in Slater Determinant. But when I googled it, some represents one electron in one column (not in one row!). Mathematically, it seems to be not wrong (since I didn't do...
16. ### Slater Determinant

I understand how to calculate the determinant. But how to construct determinant for electrons spin in an atom?
17. ### Slater Determinant

I am really really really confused how to read and construct Slater determinants :( Can someone please explain it using He at the ground state (1s2) and He at excited state (1s12s1) ?
18. ### Raman Spectroscopy

Thank you for your reply! So, anti-Stokes has lower peaks than Stokes because its initial state is an excited state where the population of electrons at excited state is lower than the ground state? Does it make sense?
19. ### Raman Spectroscopy

Why do peaks of Stokes higher than peaks of anti-Stokes in graph of absorbance unit against wave number?
20. ### Dipole Moment of Mono-nuclear

Do mono-nuclear molecules have dipole moment? If yes then, what type of dipole moment? why do they have (or do not have) dipole moment?
21. ### Zero Planck constant

Yes, I noted that. I was asking the understanding of if the Planck constant is zero. :)
22. ### Zero Planck constant

Hmm, so, if Planck constant is zero means that there is no uncertainty in both momentum and position, right? Does it mean if either one of momentum or position can be known exactly, therefore the other one is not known exactly?
23. ### Zero Planck constant

What is the effect in quantum if Planck constant is zero? Here are some points that I could think of: if Planck constant is zero, the Heisenberg Uncertainty Principles will become zero, therefore either momentum or position of a particle can be known exactly. if Planck constant is zero, both...
24. ### Particle in a box with the finite depth

For particle in a box with the finite depth, is it traveling wave? or standing wave? I am confused with its ability to pass through the potential walls that is classically forbidden area which makes me think it is traveling wave. But for particle in a box with infinite potential, I understand...
25. ### Commutator and kinetic energy

For particle in the box wave function, it is the eigenfunction of kinetic energy operator but not the eigenfunction of momentum operator. So, do these two operators commute? (or it has nothing to do with commutator stuff?) How about for free particle? For free particle, the wave function is...
26. ### Relation of pressure with mean-free-path

But how does it related with the pressure? Why is the mean-free-path high when the pressure is lower? How to explain it in term molecular level?
27. ### Relation of pressure with mean-free-path

My textbook says "The lower the gas pressure, the higher the mean-free-path". But it does not explain why. Can someone please explain it briefly? Thank you very much.
28. ### Magnetic field due to magnetic dipole

Thank you very much for your reply! I still want to make sure one more thing here. So, θ is the angle between these two unit vectors? or angle 180 degree subtract with the angle between unit vectors?
29. ### Magnetic field due to magnetic dipole

It is NOT a homework question. I am doing my revision and get stuck at this question. I am confused with the angle θ shown in this link: http://www.physicspages.com/2013/10/06/mutual-inductance/ Professor who wrote this solution stated that θ is the angle between unit vector z and unit vector...
30. ### Exploring the Work Behind EMF Generation

and one more question. Can EMF be generated through non-constant magnetic field? say, the magnetic field is changing with time.
31. ### Exploring the Work Behind EMF Generation

I understand that EMF is generated by moving a closed loop of wire through a constant magnetic field. I am confused about one thing, who is actually doing work here? (of course it is not magnetic field).
32. ### Divergence of electric field

Why is the divergence of electric field not zero for a material with non-constant conductivity?
33. ### Uniqueness of magnetic vector potential

thank you very much! I understand now! thank you.
34. ### Uniqueness of magnetic vector potential

thank you very much for the reply! As what you have explained, magnetic vector potential is not uniquely determined since there are an infinite number of equivalent vector potential A, for magnetic field B. But does it mean B also not uniquely determined since we could choose any scalar field of A?
35. ### Uniqueness of magnetic vector potential

I able to prove magnetic field is uniquely determined but I am confused how to prove that magnetic vector potential is also unique. Can I say that magnetic vector potential is uniquely determined since magnetic field has unique solution? Thanks.
36. ### Why is the magnetic field outside a toroid 0?

Place your circular Amperian loop outside the toroid. By definition, Ampere's Law states that integration of magnetic field over an amperian loop is equivalent to constant μ multiplied by current enclosed. Now, look from the top view. You will observe that current that flows at outer...