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spectrum123
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What is the conductivity of metals at 0 kelvin? i think it will be zero because at 0 k entropy is zero. Every motion is cease.
spectrum123 said:What is the conductivity of metals at 0 kelvin? i think it will be zero because at 0 k entropy is zero. Every motion is cease.
If you apply voltage anywhere on a superconductor, the voltage will be measured as a result of loss in the wires from the instrument you're measuring with. Current flow will not cause voltage drop over a superconductor, thus no heat.Drakkith said:IF we did reach 0k and you applied a voltage to the metal, then you would introduce energy and it would no longer be at 0k anyways. In as soon as you applied a voltage it would probably be a superconductor.
Low-Q said:If you apply voltage anywhere on a superconductor, the voltage will be measured as a result of loss in the wires from the instrument you're measuring with. Current flow will not cause voltage drop over a superconductor, thus no heat.
Vidar
this is wrong.Entropy is not zero at zero k (don't think about formula).it is because of Heisenberg principal because if there will not be any randomness then you can measure both position and momentum simultaneously perfectly!i think it will be zero because at 0 k entropy is zero
If everything is in its ground state, you have minimal energy and zero entropy. The uncertainty relation does not matter, it just tells you that minimal energy in quantum mechanics is above the minimal energy in classical mechanics.andrien said:this is wrong.Entropy is not zero at zero k (don't think about formula).it is because of Heisenberg principal because if there will not be any randomness then you can measure both position and momentum simultaneously perfectly!
The current will not cause voltage drop over the superconductor. Energy is in this case voltage x current. If voltage is zero the product will be zero energy. However, the voltage drop over the wires from the instrument will cause heat, but only in the wires. So you actually don't apply energy into a superconductor - only in the wires you try to tranfer that energy with.Drakkith said:I see your point. I have to ask though, if you are adding energy into the superconductor by applying a voltage, is that not related to the internal energy and thus the temperature somehow? Being a minimum energy state, I would expect that any difference in potential or current flow would make it so that the material is no longer in that minimum state.
This is wrong.andrien said:I don't think zero entropy is any proper world because uncertainty relation really matters when one deals with subatomic things.
you probably mean to those phase space element where there is certain volume of phase cell but they don't say anything about zero entropy.mfb said:This is wrong.
Entropy is defined via the states of the system - and those states already take the uncertainty relation into account.
spectrum123 said:What is the conductivity of metals at 0 kelvin? i think it will be zero because at 0 k entropy is zero. Every motion is cease.
andrien said:classical calculation does not apply as I already said.It is pointed out in feynman lectures vol. 1 that uncertainty principle must be invoked for non zero entropy.see some early chapter,it is written there.
just did not see the second page there(too hurry).I replied to the last post of page 1.Sorry for causing trouble.ZapperZ said:What classical calculation? The scattering rates are obtained using QFT!
yes,So uncertainty principle must follow from it.I don't see how it is following.Just saying it is already there,does not mean it is really there.The problem here is that people think that the HUP is a starting point in QM rather than merely a consequence.
The point is that you must either provide a reference or something equivalent,if you are saying that uncertianty principle is already taken into account.I believe in what Feynman has said that if uncertainty principle is taken into account then entropy must not be zero at zero temperature.I mean, where is your point?
andrien said:The point is that you must either provide a reference or something equivalent,if you are saying that uncertianty principle is already taken into account.
ZapperZ said:2. Undergraduate level.
The conductivity is expected to be infinite, i.e. resistivity approaches zero. This is because the predominant source of resistivity (lattice vibrations) diminishes to zero (theoretically) at T=0.
Zz.
just an index does not mean any quantum property.Also I have done sakurai some time ago,it does not say anything useful for it.It seems the kind of reference you're after would have to be a general proof of the uncertainty principle, since the 'i's label quantum states, which necessarily satisfy the HUP. I'm sure most QM textbooks will give a derivation. Try Sakurai, Modern Quantum Mechanics second edition for example.
wiki says'This upholds the correspondence principle, because in the classical limit, i.e. whenever the classical notion of probability applies, this expression is equivalent to the familiar classical definition of entropy'(gibbs one).Hence von Neumann's expression reduces to Gibbs expression.
It is possible to calculate that all physical wavefunctions satisfy the (p,x)-uncertainty principle. This is related to the mathematics of Fourier transformations. Alternatively, it is possible to derive it in a pure algebraic way as well. Read some introduction book about quantum mechanics, or see Wikipedia for the general concepts.andrien said:yes,So uncertainty principle must follow from it.I don't see how it is following.
Source?I believe in what Feynman has said that if uncertainty principle is taken into account then entropy must not be zero at zero temperature.
mfb said:It can be different from zero (with a degenerate ground-state), but it does not have to.
every one knows that.It is possible to calculate that all physical wavefunctions satisfy the (p,x)-uncertainty principle. This is related to the mathematics of Fourier transformations. Alternatively, it is possible to derive it in a pure algebraic way as well.
It been time.I think it was written in vol. 1 of his and early chapters.Source?
andrien said:I think it was written in vol. 1 of his and early chapters.
psmt said:i would have expected better of Feynman!
The conductivity of metals at 0 Kelvin, also known as absolute zero, is zero. This is because at this temperature, the atoms in the metal are not vibrating and there is no movement of electrons, which are responsible for conducting electricity.
As mentioned earlier, at 0 Kelvin, the atoms in the metal are not vibrating and there is no movement of electrons. This lack of movement makes it impossible for the electrons to flow and conduct electricity, resulting in a decrease in conductivity.
No, all metals will have zero conductivity at 0 Kelvin. This is a fundamental property of metals at this temperature and cannot be changed.
The lack of conductivity at 0 Kelvin makes metals unsuitable for use in electrical applications at this temperature. However, metals are often used at higher temperatures where their conductivity is not affected by the lack of movement of electrons.
Yes, studying the conductivity of metals at 0 Kelvin helps us understand the fundamental properties of metals and their behavior at extreme temperatures. This knowledge can be applied in various fields, such as materials science and engineering, to develop new materials with specific properties.