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What is the magnetic effect on an electric current.

  1. Jun 25, 2012 #1
    I was just wondering and I looked and couldn't find anything. I suppose i could experiment it my self but anyway.

    If I had a wire with an electrical current flowing through, just say 10Amp; and I pass a magnet near the wire, would it slow the current down? Or increase the resistance? I know a solenoid has an effective resistance, that can be derived from its Inductance in Henries.

    Also if there is an effect, would the effect be greater if I wrapped the wire in a coil around the magnet.

    So I am asking, is there an effect? If so by how much? and how can it be calculated using equations?

    Thanks for some future replies. :)
  2. jcsd
  3. Jun 25, 2012 #2


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    There will be no effect on the current, but the wire will deflect from its starting position.
  4. Jun 25, 2012 #3
    Ok, thank you for replying.

    Ok so just for saying I have made a generator that has magnets in it. And I believe that magnets wear out overtime, therefore their effective pulling/pushing forces will decrease; meaning less power output. Could I then regenerate/magnetise said magnets if I removed them and placed them just say in a copper or/steel/iron pipe with wire wrapped around.

    Am I right in thinking that if i got the current generated from the generator passed through a wire which is wrapped around a pipe with magnets in them it,would it re-magnetise the magnets to full potential, without reducing the current/voltage/power/watt generated from the generator? and would this over heat the wire ( obviously with current through it would) any further than it would with out magnets in them.

    I am only asking because If I were to build a generator, I would love to save any energy, than I can; so instead of re-magnetising the magnets in a different circuit with a separate power source, I could use the own generators electricity.

    Also I am wrong about re-magnetising magnets this way what would the best way be, because I would think that the flowing current and magnetism the coil will create will re align the magnetic domains making the field stronger again.

    Thanks for replying and replying in the future if you kindly would. :)
  5. Jun 26, 2012 #4


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    You have no hope of rejuvenating the sort of magnets you would want to put in any generator that you'd want to make; they require extremely high fields in their manufacture. But they do last a very long time if you don't actually bash them or roast them. There is no reason for them to get 'weaker' when used in the generator because they don't supply any energy - that is supplied by turning the handle.

    Some generators use electromagnets. Automotive alternators and the massive ones used to generate mains electricity use electromagnets (field windings) because their field can be controlled and the output voltage regulated. Permanent magnets can be made with very high strength, these days, and are used in most small generators. They have a big advantage in that they need no electrical power to get them started!
  6. Jun 27, 2012 #5
    Ok, 2 questions, Would putting them in a coil to recharge them, work? Never mind how slightly.

    The next one is, Do you know them amount of energy that can be produced per magnet. For example. A small wind turbine might have 10 magnets in it, and in its life time it could genererate 10 mW of energy. So 1mW per magnet. So would the amount of energy needed to bring it back to strength be more equal or less than 1mW of energy needed.

    So if it does requiere more, would putting these depleted magnets in a coil be sufficient enough to saturate them?
  7. Jun 27, 2012 #6


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    'Fraid not. It's all or nothing.
  8. Jun 27, 2012 #7
    Sorry, I dont understand what you mean.
  9. Jun 27, 2012 #8


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    It takes an enormous field to have any effect at all. Then they all go over with a bang and stay there. That's what makes a permanent magnet material different from iron.
  10. Jun 27, 2012 #9

    jim hardy

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    Mr sponge you might want to familiarize yourself with magnetic terminology. Google can be you friend, it's just a matter of gettng some good buzzwords to search on.
    Ty these two links for starters.

    my hometown has a small magnet factory where i have watched them " charge" magnets. They do have some control over how strong they leave the magnet by how hard they 'push' it with the magnetizing coil.

    Sophie is right it takes a large apparatus. One could be home-made , but you'll find today's magnetic materials are indeed permanent and very difficult to demagnetize. This was not always so. Pre WW2 most towns had a shop that could recharge the magnets in tractor ignition magnetos.

    Regarding your original question - look up "Hall Effect".

    old jim
  11. Jun 27, 2012 #10
    Sorry, i am quite famillier with the terminology, I am studying it as part of my engineerring course at a A level. I was just wondiring if it would create resistance in i put a magnet in a coil. Or whether it would charge it at all.

    I know that they say, if you want to make a bar magnet stronger you can use a neodymium magnet and stroke it with it so it would re align the domains. Therfore I belive that if i put a magnet in a coil, the current will re align the domains.

    To be honest, since I started to learn about magnets, generators and motors, a help who knows alot about electronics, were telling me stories of supposed magnetic motors that are perpetual. I know about the law of thermo dynamics and i have looked at a few videos and i was wondering if they mangaged it to spin with magnets without losing speed ( not imposible), I think where is the magnets getting the energy from. I know manetsism isnt energy as such, but it takes energy to make a magnet. So these machines rnt perpetual unless if they can generate enough electricity tht could eventually reharge the magnets when they have depleted.

    Here is a video of such machine working and is well made and no hidden compartments. It lookos quit convincing, but I am just thinking what about when the magnets deplete.

    So I am still asking the question how much energy is required to charge a magnet. Is it equal or less or more than needed to charge it in the first place.
    Last edited by a moderator: Sep 25, 2014
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