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Homework Help: Making an Electromagnet to carry 1kg

  1. May 19, 2014 #1
    1. The problem statement, all variables and given/known data

    To create an electromagnet capable of carrying 1kg without it being too dangerous i.e utilizing a car battery.

    2. Relevant equations
    Strength of electromagnet is dependent on number of turns and current.

    3. The attempt at a solution
    Used hot galvanized (I assume steel) nail and spike, wrapped with enamel coated copper connected to 3 battery packs (each with 4 D batteries in series). Experimented wiring the batter packs in series and parallel. These attempts were not that great and resulted in only a few paperclips being picked up.

    Second take on the project I took was taking apart a power adapter to take out the transformer and re-arranging the "E" pieces of metal to all face one way and hooking that up to a battery though I failed and severed the copper wires when removing the plates.

    Basically, would the transformer approach be the best way given that it must carry 1 kg. And if so, I'm still a bit confused as to where to connect the current to it.

    Thanks for reading
  2. jcsd
  3. May 19, 2014 #2


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    You should do some calculations before you start tinkering with the equipment. How much force do you need to pickup 1 kg? How big a magnetic field do you need? How much current can your batteries produce? What kinds and shapes of cores are available? These are only a few questions that you should answer first. Once you know the answers you can come up with a design that meets the requirements, at least theoretically. Then, and only then, should you start tinkering. There is no point wasting time cobbling something together if, even if it worked perfectly, it would not meet the specs.
  4. May 19, 2014 #3
    That's actually a good idea, I don't know why I didn't think about doing equations first...

    To lift 1 kg, is about 10 N of force.

    Currently only have a straight rod of Hot galvanized steel, which isn't ideal but has to work. I'm trying to find a U-shaped piece as that should help.

    From what I gather you can gather 1 amp out of a D battery. Though apparently this changes depending on freshness and etc. Though I'm also not too sure on how the resistance of the wire will affect this also.
  5. May 19, 2014 #4


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    Staff: Mentor

    I think you do a lot better if the end of the magnet and the object to be lifted both have large highly polished surfaces that meet perfectly (making atom-to-atom contact throughout). The more your setup departs from the ideal, the less effective the magnet will be.
  6. May 19, 2014 #5


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    Batteries are rated in amp-hours. D batteries have about 2 amp-hours, more or less. It varies not only by freshness, but also by brand and presumably cost.

    Ohm's law, but consider reactance, not just resistance. And be careful of short circuits.
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