Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Temperature fluctuations in helium

  1. Jan 24, 2017 #1
    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! :)
     
    Last edited: Jan 24, 2017
  2. jcsd
  3. Jan 24, 2017 #2

    anorlunda

    User Avatar
    Science Advisor
    Gold Member

    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.

    in-phase.jpg

    Your experiment sounds like fun.
     
  4. Jan 24, 2017 #3
    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!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Temperature fluctuations in helium
  1. Inhaling helium. (Replies: 23)

  2. Pressure of helium (Replies: 1)

  3. Helium at 0K? (Replies: 3)

  4. Helium 3 (Replies: 4)

Loading...