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Homework Help: I am dumb!

  1. Jan 30, 2010 #1
    1. The problem statement, all variables and given/known data

    For an electromagnet that is just made up of wires and a core, what power supply can I use other than batteries that let me adjust the volts? Can you explian in detail?

    2. Relevant equations none

    3. The attempt at a solution I have already looked on the internet for power supplies, but I am still confused.
  2. jcsd
  3. Jan 30, 2010 #2


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    Well, standard laboratory DC power supplies have adjustable outputs over a very wide range, but I imagine that they are probably too expensive for a hobbyist (still, you can look into it and see if there is anything at the cheap end of the scale that would work).

    Maybe it would help if you knew how some of them work and what they are called, so that you can more easily Google them. There are different kinds of commercial power supplies, some are adjustable, some are not. I think you could look into a switched-mode power supply (like what they use in computers -- maybe you could find a computer power supply from a computer parts distributor?) It plugs into the wall and produces a DC output. A transformer + rectifier could do the same thing (this is an older and less fancy type of power supply), but I'm not sure if you want to play around with that.

    For solutions involving batteries -- if the problem is to be able to adjust the output voltage, you could create a simple resistor voltage divider in which one of the resistors is a potentiometer (i.e. a resistor whose resistance is adjustable). This requires the ability to build rudimentary electric circuits. If the problem is to maintain a constant voltage in spite of a draining battery, you could start out with a battery that has a much higher voltage than what you need, step it down, and then use something like a zener diode to maintain that output voltage constant (at least until the battery drains below the point at which the circuit stops working). This requires some knowledge of electronics.

    Then again, what you really need for an electromagnet is a constant and sufficiently high current through the coil. There are ways of achieving that using electronic circuits as well, but I don't know how much knowledge you have about electronics.

    As a disclaimer, these are just ideas that came to mind, off the top of my head. I don't necessarily have first-hand experience with all of them. There are safety concerns. Make sure you fully understand what something is and how to use it before you just buy it and plug it in.
  4. Feb 1, 2010 #3
    This is great advice. Any other suggestions?
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