Do SuperFluids respond to Magnetic Fields?


by BrianConlee
Tags: charge, magnetic field, movement, superconductivity, superfluid
BrianConlee
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#1
Sep20-08, 08:10 PM
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I can't seem to find any real information on this, so maybe this is the place to get it.

Ok, we know Superconductors repel magnetic fields. We know anything with current running through it produces a magnetic field according to the right hand rule. Obviously this is how superconducting magnets work.

Now, how does a superFLUID respond to a magnetic field? Can it's motion be influenced? Can it hold an electric charge and be moved by a magnetic field?

I'm running into what I might think is an obvious conclusion here: superconducting magnets are cooled by liquid helium, some of them anyways, and I'm guessing that the liquid helium is in a superfluid state? Another thing I'm not sure of actually.

If anyone can help I'd really appreciate it.

Thanks!
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BrianConlee
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#2
Sep20-08, 08:13 PM
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OH, one more question:

Is there a liquid superconductor?

Make that two questions:

can you propel a superconductor to high speeds (not talking about c here, just (excuse my laymen term) pretty quick) without loosing superconductivity?

And one for the road:

Can you propel a superfluid to high speeds without loosing superfluidity?
granpa
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#3
Sep20-08, 09:23 PM
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<link deleted by Doc Al>

http://www.britannica.com/EBchecked/...#ref=ref921912

olgranpappy
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Sep20-08, 09:33 PM
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Do SuperFluids respond to Magnetic Fields?


Quote Quote by BrianConlee View Post
Can you propel a superfluid to high speeds without loosing superfluidity?
No. There's a critcal flow velocity above which the fluid is not super. What exactly the critical velocity is depends on the excitations of the super fluid. Usually people begin discussions of the excitations by considering "phonons" and "rotons", but actually (if I remember correctly) it is the creation of vortex rings that is the limiting factor in determining the critical velocity.

As for your other questions... Regarding superconductivity try the book "Introduction to Superconductivity" by Tinkham. Regarding superfluids there is some discussion in Landau and Lifgarbagez "Statistical Mechanics II". Also for superfluids see "The Theory of Quantum Liquids Vol. II" by Pines and Nozieres.
granpa
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#5
Sep21-08, 10:02 AM
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Dear granpa,
You have received a warning at Physics Help and Math Help - Physics Forums.
Reason:
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General Information
Please be careful with the links/reference that you post, making sure that you only link to scientifically mainstream sites. *(Your first link points to a site that is clearly some kind of religious/mystical/spiritual site, which is not an appropriate reference for PF.)
-------

my apologies to the forum. I will have to check my google results more carefully next time. here is the EXACT SAME ARTICLE:
http://en.wikipedia.org/wiki/Superfluidity#Background
BrianConlee
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#6
Sep21-08, 11:34 AM
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Thanks for the responses thus far, but I've only been able to find what I already knew.

(Except for the rotational speed, that is VERY helpful)

Again: How does a superFLUID respond to a magnetic field? Can it's motion be influenced? Can it hold an electric charge and be moved by a magnetic field?

ANy additional help would be....... helpful.
BrianConlee
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#7
Sep21-08, 11:35 AM
P: 65
Almost forgot
Is there a liquid superconductor?
can you propel a superconductor to high speeds (not talking about c here, just (excuse my laymen term) pretty quick) without loosing superconductivity?
olgranpappy
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Sep21-08, 10:12 PM
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Quote Quote by BrianConlee View Post
Thanks for the responses thus far, but I've only been able to find what I already knew.
So... you already knew everything that was in the books I mentioned?
olgranpappy
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Sep21-08, 10:17 PM
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Quote Quote by BrianConlee View Post
Almost forgot
Is there a liquid superconductor?
not that I know of... but I'm not an expert in the field.

can you propel a superconductor to high speeds (not talking about c here, just (excuse my laymen term) pretty quick) without loosing superconductivity?
Presumably, yes... since the whole thing is Galilean Invarient.
granpa
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#10
Sep22-08, 03:59 AM
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first of all I am not an expert.

speaking intuitively I would say that superconductivity should probably be renamed superdiamagnetism.

even though helium is obviously slightly diamagnetic I rather doubt that superfluid helium is superdiamagnetic (I could be wrong). superfluidity probably has more to do with phonons than with electron spin.
ZapperZ
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#11
Sep22-08, 08:32 AM
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Hg is the only superconductor that I know of that is a liquid. It was also using Hg that superconductivity was first discovered.

A superfluid (as in a neutral superfluid such as LHe) does not respond to external magnetic field, unlike a supercurrent in a superconductor. The vortices that are observed in superfluids are thought to be due to "defects" in the superfluids. In LHe, liquid phase is thought to be made up of two interpenetrating components - the superfluid and the normal fluid. It is this defect that causes the formation of such vortices, not magnetic field, which is the cause of the vortices in Type II superconductors.

Zz.
weejee
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#12
Sep22-08, 08:52 AM
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Quote Quote by ZapperZ View Post
Hg is the only superconductor that I know of that is a liquid. It was also using Hg that superconductivity was first discovered.
Zz.
I guess it becomes a solid well before reaching T_c.
ZapperZ
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Sep22-08, 09:02 AM
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Quote Quote by weejee View Post
I guess it becomes a solid well before reaching T_c.
You're correct. I should have said that it is a liquid at room temp, but not when it turns into a superconductor.

Zz.
LURCH
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#14
Sep22-08, 11:58 AM
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Quote Quote by BrianConlee View Post
Again: How does a superFLUID respond to a magnetic field? Can it's motion be influenced? Can it hold an electric charge and be moved by a magnetic field?

ANy additional help would be....... helpful.
You are right about how hard it is to find ifnormation online about this. I'm going to suggest that it is not possible by any known means, for two reasons:

1) If there was a known way to do it, someone would be doing it, and publishing their results, and these published results would not be hard to find.

2) As far as we know, superfluids can only exist at very low energies (temperatures). Any influence one might attempt to have on a superfluid with a magnet would involve an input of energy, in which case it would no longer remain a superfluid.
BrianConlee
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#15
Sep23-08, 08:05 PM
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Thank you everyone for your wisdom and help. I didn't mean to sound arrogant with the "I already knew" comment, sorry bout that.

Here's my next question while we're on the topic, I hope I'm not made to change threads since I have some great thinkers helping me out.

Since magnetic fields are out of the question, how is it I could propel a superfluid? I'm guessing ionization is out of the question. (to make the superfluid atoms charged) but perhaps an applied electric field, via a piezo electric field, could charge it instead of plasma-esque temperatures? I know they can use the laser/light 'heat engine' approach, but this is more of a fountain effect and not so much a moving current effect.

I'm truly stumped, so I guess I'll go ahead and fill all of you in on my thoughts.

I know they've been doing the spinning super conductor experiments and possibly manipulating gravity (smoke rings) and I was trying to figure a way to channel superfluid around a torus. NOT around the torus in a circular particle accelerator motion, but morso around the outside and through the inside... like the magnetic field direction generated by a moving electrical current (why I was asking about magnetic manipulation.

Boy, the lack of friction is a godsend... but truly an engineering/physics challenge!

Any thoughts?
I just read that they've been able to bring hydrogen to a superfluid state, could this be helpful?
ZapperZ
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Sep23-08, 08:18 PM
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Quote Quote by BrianConlee View Post
I know they've been doing the spinning super conductor experiments and possibly manipulating gravity (smoke rings) and I was trying to figure a way to channel superfluid around a torus. NOT around the torus in a circular particle accelerator motion, but morso around the outside and through the inside... like the magnetic field direction generated by a moving electrical current (why I was asking about magnetic manipulation.
You should never build an idea on top of something as dubious as this. The Podkletnov effect has never been verified and is not considered as valid physics.

I also suggest you re-read the PF Guidelines before proceeding any further. Pay particular attention to speculative, unverified theory. Before you use something, make sure you understand first the basic principle. You simply cannot go on extrapolating something that hasn't been shown to be valid.

Zz.
BrianConlee
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#17
Sep25-08, 04:45 PM
P: 65
ZZ,

Sorry about that. I'm a little new to the forum and this is actually my first thread!

Anyhow, I didn't realize those results hadn't been confirmed and that they were actually fringe physics; however I do believe that I've read about them being repeated. Either way, are you sure that there's absolutely no evidence that spinning super conductors or super fluids can generate gravitometric fields? And also, what source can I use to determine the validity of any given physics theorem?

Thanks again!
olgranpappy
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#18
Sep25-08, 09:27 PM
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Quote Quote by BrianConlee View Post
And also, what source can I use to determine the validity of any given physics theorem?
Well, there certainly is no oracle to which one can appeal for the truth.

Ultimately, any physics "theorem" must be held accountable to experimental facts.

P.S. In these kinds of endeavors some well-honed critical thinking skills can be very useful. See, for example:
http://en.wikipedia.org/wiki/The_Demon-Haunted_World


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