Temperature fluctuations in helium

[Kara386]

I'm about to do an experiment on second sound in superfluid helium. Reading the lab manual it says we will generate it by putting a heater into the fluid and then passed an AC current through it. What we are going to measure is apparently the 'normal fluid fraction', which I guess under the two fluids model is the non-superfluid part. Weird thing: there's a casual mention that it should propagate away at twice the frequency of our current! Why would that happen?? I was trying to find some equations that would describe this behaviour but I can't, or at least those on the internet are way beyond me.

Thanks for any help! :)

 

[anorlunda]

See the PF Insights article, AC Power Analysis: Part 1, Basics

From the article, V(t)*I(t) is the instantaneous power. When V and I are in-phase, V*I is double the fundamental frequency.

Your experiment sounds like fun.

 

[Kara386]

See the PF Insights article, AC Power Analysis: Part 1, Basics

From the article, V(t)*I(t) is the instantaneous power. When V and I are in-phase, V*I is double the fundamental frequency.

Your experiment sounds like fun.

I see, thank you! Yeah, it'll be a good experiment I think. In particular looking forward to using lots of liquid nitrogen, the safety briefing was just packed with interesting ways to go wrong!