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

Einstein -de Haas Effect

  1. Jan 6, 2005 #1
    How do I replicate the Einstein - de Hass Effect experiment? I know the basic premise: hang a slender iron rod inside a ring magnet and it should spin as the electrons all line up, to conserve angular momentum. Are there any websites detailing how to conduct/build/recreate this experiment? I've tried several times to find any and got zilch each time. So I moved on to experimenting. I've tried several ways, including using fishing line (can't make it taut enough to not shift to one side as the line stretches); swivels soldered to the ends of a rod and connected to hooks while the magnet sits on a wooden base (the tension breaks the solder, even JB Weld won't hold, and it's really tough to get an absolutely straight connection across a weld). I've also tried iron magnets and rare earth magnets (use gloves when handling these--there's a safety lesson in there somewhere). Now I'm going to try fixing the rod inside bearings at either end to hold it rigid. The bearings are fixed to a structure and the magnets will sit on a wooden beam midpoint along the rod. Am I barking up the wrong tree?
  2. jcsd
  3. Jan 6, 2005 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I've never heard of this before...strange. I know of the de Haas-van Alphen Effect, and the Shubnikov-de Haas oscillation, but not this one. Looks like de Haas has immortalized himself through great collaborative work.

    Anyway, I found a kit (for sale) that reproduces this experiment. The kit is made by the Physics Demo group at the University of New Mexico. You can either try and speak to someone there, or simply buy the kit to see how it's built.


    Can't do better than this right now, but someone is sure to come along with better advice.
  4. Jan 7, 2005 #3
    Thanks for the info. It seems amazing that for someone as famous as Einstein (and De Haas) that this chapter has gone pretty much unrecognized. Maybe it's just not important (unless you're trying to duplicate it).
  5. Jan 11, 2005 #4
    The experiment is not unrecognized or unimportant. The magnetomechanic ratio tells us about the orbital moment of the electrons involved in magnetism. Now there are also other ways of measuring this, but these methods require more theory and are less direct.

    X-ray magnetic dichroism gives reasonable agreement with Einstein-de Haas data:
  6. Jan 12, 2005 #5
    Pieter; Unless you're a physicist, I beg to differ. I've tried numerous searches through Google, Gallileo (Ga University Library System), local library, etc. All I got for my trouble was a quizzical look (most of the time), some Japanese briefings, a description of properties for magneto-optical drive calibration, and only through this site an actual picture of a duplicate of the experiment. Even the Einstein archives doesn't have it in English (unless you're willing to fork over a membership fee, maybe-I wasn't able to convince my wife that was a necessary expense to find out).
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook