Liquid Helium II the superfluid (part 3 The superfluid has zero viscosity)

A 1963 film by Alfred Leitner demonstrating the remarkable properties of liquid helium when cooled below the lambda point (the superfluid state). The superfluid is able to flow without viscosity through the smallest of holes.

Category:

Science & Technology

Tags:

• Superfluid
• helium
• entropy
• viscosity
• Leitner
• Physics
• statistical
• mechanics

[Pinkishbass91]

How can there be a Normal component? Cause if so wouldn't it stay in the beaker when using the capillary flow experiment?

[Zantorc]

@Pinkishbass91 No. The ratio of normal to superfluid component is determined by the temperature. It's a dynamic equilibruim not a static one. You can think of atoms as contantly going between normal and super state. As the superfluid flows out, the flow from normal to super will be larger than the flow from super to normal. That's why it all drains out. The superfluid is always draining away and getting replaced as the normal component transforms to super component.

[Desmonddd2002]

@Zantorc ironically if u have finished watching ur own videos u would know that the normal component/superfluid component explanation of Helium does not stand. So is everyone here pretending to be experts and talks about "normal phase" and "superfluid phase". I am no expert at quantum mechanics but is only repeating what the scientist sed at the end of pt. 6. According to him Liquid helium II is in both state simultaneously, and the two phase "classical" model is inadequate in explaining it

[Zantorc]

@Desmonddd2002 The 2 fluid model is more of a phenomenological explanation, so in that sense it's 'wrong'. But it's soundly based and correct, it's just not a complete explanation. It explains most macroscopic phenomena, you just have to know its limitations.

[Zantorc]

@genius1140 'This "scientist" is stupid'

Have you considered that it might be you who is stupid? That perhaps Professor Leitner knows a bit more about physics than you?

[Zantorc]

@genius1140 Then you ought to be aware that your argument does not apply to the superfluid component - it is not a Newtonian liquid. Furthermore at absolute zero there is no normal component left it is entirely superfluid.

Your error is to fail to appreciate that viscosity measured by bulk flow and capillary flow give different answers and that for one to be zero and the other nonzero is a paradox. A paradox which cannot be resolved except by quantum mechanical arguments.

[Zantorc]

@oscargortez A superfluid would flow past any imperfections without friction. Also notice any motion in fluid cant transfer from one part of the fluid to another by normal viscous means and there is a vertical separation between any flow and the paddle wheel. In theory a toy boat in a superfluid bath would remain stationary when you put the motor on - in practice this extreme case is more complex.

[oscargortez]

@Zantorc I'm not scientist but, for the second experiment to be legitimized wouldn't the cylinder that's spinning need to be perfectly smooth? Couldn't the current being caused, simply be a result of the fluid being 'pushed' by the imperfections of the cylinder? Sure that wouldn't really mean anything for normal fluid, but um, liquid helium II isn't normal is it? Just a thought.

[painxtreme]

@Sierrafox17 Again, no, Superfluid Helium has NO viscosity, that is one of the criteria that defines it as a superfluid. Once it goes below Lambda, no viscosity or resistance. You can run 1,500 Amperes through a 1 mm or less copper wire, cooled by superfluid. If it goes above lambda....well ask the Cern people what happens if your helium gets a half degree too warm. Normal house wiring could not come close to taking 1,300 Amps. Your house, if like most modern ones has only 200 Amp service.

[painxtreme]

@Zantorc Perfect and concise. I guess the "genius" awards had gone to very lax standards before they handed out the 1,140th one.

[Filiostoutheou]

@Zantorc yep one thing every physicist should know is that 'super' anything, like superconductivity, typically does not follow the basics of Newtonian physics which is why they are such researched phenomena .....Im surprised he still came back saying that he did not speak in error. It's not hard to do a little extra research.

[x65535x]

@genius1140

It's funny how in the video Professor Leitner specifically speaks about the fact that there should be no Newtonian reactions seeing as it doesn't satisfy being a Newtonian fluid.

Betcha didn't think anyone would call you out on it, that most people would just say, hell, big words, fair grammar, and decent spelling, he must be right.

[mikeyrules1992]

But the problem is that no matter how small we are talking about, when one item smashes another item there is transfer of energy. The top of the motor may seem smooth, but down to microscopic levels it is as rough as the Alps. There for there is a constant transfer of energy from the surface of the motor, as it collides with atoms that collide with more atoms and so on. This transfer of kinetic energy could easily be what caused the paddles to turn. And no this "scientist" is in no way "stupid."

[b1keboy]

This guy be baked! ; p