Superfluidity is a very rare phenomenon that occurs at ultra cold temperatures. It is only observed in Helium because only Helium stays a fluid at that temperatures. Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without loss of kinetic energy.
Say you have a container of gas. You keep removing energy from it. In other words, you are cooling it. You remove so much energy that now all the atoms go sit in the lowest energy state. Seeing that they are already in their lowest energy state, nothing else can now remove energy from it for eg: neither gravity nor friction. Which is why if you hold superfluid helium in a container, it will spontaneously flow out (creep along side the walls of the container). If you look at the image below, you can see a drop at the bottom. It is because of this sort of creeping that climbs up the inner wall, flows along the outer wall and collects at the bottom (center) as a drop.
Say you have a container of gas. You keep removing energy from it. In other words, you are cooling it. You remove so much energy that now all the atoms go sit in the lowest energy state. Seeing that they are already in their lowest energy state, nothing else can now remove energy from it for eg: neither gravity nor friction. Which is why if you hold superfluid helium in a container, it will spontaneously flow out (creep along side the walls of the container). If you look at the image below, you can see a drop at the bottom. It is because of this sort of creeping that climbs up the inner wall, flows along the outer wall and collects at the bottom (center) as a drop.
It also displays other remarkable properties such as having no measurable viscosity. Viscosity is a fluid’s response to shear stress which can also be understood as a fluid’s internal resistance to flow. Naively said, this is how “sticky” a fluid is. For example, Oil is more “stickier” than air and hence more “viscous”. This viscous nature is important because it helps fluid molecules “stick” to other things and to each other. If for example air were not viscous, turning on the fan would have no effect since air molecules would not stick to the fan thus the fan cannot impart kinetic energy to the air and hence it cannot move and cool you.
Coming back to the topic on hand, the superfluid has no measurable viscosity, so if you put a fan inside a container of superfluid and have something else placed in the fluid, it shouldn’t feel the effect of the fan inside.
Some more amazing things about Superfluid are :-
1.) The superfluid state is its own state of matter, the Bose Einstein Condensate.
2.) Superfluid Helium has zero entropy!
3.) Helium never solidifies at normal atmospheric pressures.
No comments:
Post a Comment