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EMF generated by solenoid around hollow Iron core?

  1. Nov 2, 2016 #1
    I'm currently in conceptual phase of designing a coil gun. Thinking back to my physics 2 class-- and some of my independent studies-- I understand an EMF produced by a solenoid with current through the wires of it is strengthened significantly by a ferrous core, as seen by the classic experiment in which a copper wire is wrapped around a nail, and the nail becomes magnetized.

    Would this concept apply to a solenoid wrapped around a hollow iron tube? In other words, would a solenoid wrapped around a hollow iron tube have a stronger EMF as compared to a regular air-coil?

  2. jcsd
  3. Nov 2, 2016 #2


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    Staff: Mentor

    Welcome to the PF.

    No, the hollow ferrous tube would shield its interior from the B-field generated by the coil.
  4. Nov 2, 2016 #3
    Okay, but why? How would the B-field be affected by the introduction of a hollow tube? I understand the Meissner effect but that is applicable to superconductors. Is it because the wires will conduct current through the ferrous tube and force the B-field around the tube?
    And thank you for the welcome. I hope to learn a lot here and maybe even help others if possible.
  5. Nov 5, 2016 #4

    Stop reading about cool and interesting things like superconductors and focus on "boring" stuff like linear algebra and hysteresis losses. :biggrin:
    Coilguns are a great starter project for electronics hobbyists. You learn first-hand about Maxwell's equations, high-voltage power supplies and safety, capacitors and how disappointing reality can be compared to your imagination.

    But I don't know what you hope to achieve with this project (it IS quite involved). So do you want a realistic and instructive coilgun project - or do you want to go straight to DARPA level velocities and performance?
  6. Nov 5, 2016 #5
    Haha, my limited knowledge of superconductors is only from research I did for an engineering class last year. Currently learning linear algebra but have yet to learn its applications in physics. Perhaps that is something I should look into a bit more, as well as hysteresis losses. Any tips on where to start?

    As for reality vs imagination, I like to know what the bounds of the physical world are before I even draw any expectations. My current expectations are only to get an object to move through a coil and then to go from there. Anything beyond that is merely my curiosity trying to figure out what I can and cannot do, as well as how things do and do not work. Most learning experiences come from being wrong, which is completely okay in my mind. Whether I can or cannot achieve what I'm asking doesn't really matter to me, as long as I'm learning something from it. I want to get as involved with this project as my resources allow to be honest. I think this could be a fantastic opportunity to apply some of the knowledge I've gained in school so far, and see the differences between concept and reality.

    Also, DARPA level velocities sound fun as hell. But I have to start somewhere don't I? :-p
  7. Nov 6, 2016 #6


    Staff: Mentor

    There are dozens of "DIY coilgun" videos on YouTube. Did you look there first?
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