1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Electromagnetic Lasers

  1. Jul 26, 2009 #1
    My roommate and I are working on a backyard physics/engineering project, with the intent to hopefully scale it up to massive proportions. One of the issues we recently came across, though, was the matter of focusing our electromagnets for both efficiency and to keep from effecting anything else.

    I realize that magnetic fields roughly resemble a torus, and thus are inherently radial in their growth, but if we could figure out something to do to hieghten it and keep it from getting proportionally wider, it would solve one of our large problems.

    Any thoughts?
  2. jcsd
  3. Jul 26, 2009 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    You incorrectly assume that we know what you are talking about. Please restate your question with some indication of what you are trying to do.
  4. Jul 26, 2009 #3
    If I understand this right...

    You can only 'focus' radio signals with aerial arrays or parabolic dishes and the more 'focusing' (gain) you want the bigger those have to be.

    You can't invent you way out of that. You can't make a small parabola work like a large one. Why do you think they need to construct massive dishes for radio-astronomy?

    I would suggest you are wasting your time.
  5. Jul 26, 2009 #4
    We're trying to create what amounts to an electromagnetic jack, having a series of rotating, electromagnets in a bowl shape, with some sort of potentometer or rheostat to control ascent, and a semisphereical peice of ceramic with an inch-thick aluminium plate over the flat part and neodynium magnets across the curve on the bottom.

    Our mock-ups work fine, but as we increase the power to the electromagnets to get the platform higher, the field gets bigger and problems begin arising (a dead digital watch stands as our only victim thusfar).

    As far as I know, electromagnetic fields can be modeled in a series of torus with the inner edge remaining constant at the source of the field, and the central point of the rotated circle moving outward to represent the distinctly weakening layers of the field.

    I want to find a way to generate an electromagnetic field where instead of the field layers resembling torus (circles rotated on an off-axis), they resemble (non-circular) ellipses rotated on an off-axis, in such a way that the foci and focal distance can be changed.

    In short: I want to create an electromagnet that can deliver more push at a further range, without the field growing larger at the sides. I don't mind that the back end pulls at the greater range, as we can get around that.
    Last edited: Jul 26, 2009
  6. Jul 26, 2009 #5
    Interesting concept, Moe. Not exactly sure I can see the full nature of your device; I assume you are using static magnetic fields as a lifter. One of the best ways to shield the static magnetic field is to try to put mu metals around the edge of the device (to try to limit the lateral expansion)...and then ramp up the interior.

    Mu metals are an effective way to shield high B fields....NASA does it all the time :biggrin: Not exactly cheap, but it works.

    See here: http://www.lessemf.com/mag-shld.html

    and for some background: http://en.wikipedia.org/wiki/Mu-metal

    Last edited: Jul 26, 2009
  7. Jul 26, 2009 #6
    The mu-metals look quite nice, and a more than adequate solution to our problem (and a few others we were having) for the time being. I don't know what kind of current we'll use down the road, but since we do have a DC set up going right now (a transformer charging into a bank of pretty hefty capacitors and a varistor as the valve out to the 28 electromagnets) I'm pretty sure we have a static field.

    I'm an engineering student, and my roommate is a physics major, so I'm not quite as well versed in electrostatics and magnetism as he is, but I do try.

    As to the nature of the project, could you think of any interesting large scale applications for an electromagnetic "lift" that could steadily push something up to ~80mi? :) We both got a little tired of NASA's space elevator idea using a carbon-fibre ribbon, and came up with this.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook