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Tried making a telegraph What am I doing wrong?

  1. Jan 16, 2012 #1
    Here is how I set it up:

    I am using 22 gauge hookup wire, all of the metal is steel (magnetic), and the nail in the electromagnet part is iron.

    Am I connecting the wires to the wrong metal parts, or doing so incorrectly? I found this set up at: http://w1tp.com/perbuild.htm

    Please help, I am so lost :(
  2. jcsd
  3. Jan 16, 2012 #2


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    Try holding a nail very close to the coil at one end. If you can feel the nail move when you turn the current on and off, the rest of the circuit is probably working OK.

    If you have a magnetic compass, that should give a strong indication when it is held near the coil.

    This circuit is very rough on batteries, so you would need almost new batteries to make it work.

    The metal being attracted to the coil needs to be very close to the coil core to get much attraction. So, if possible, bend your metal so that it is very close to the end of the coil.
    This will mean you have to shape the metal to also get proper switching action.
  4. Jan 17, 2012 #3


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    That 'bendy' bit of metal (are you sure it's steel? Aluminium won't work.) looks a bit thick / stiff and it's a long way from the solenoid. You may just be short of magnetic field to make it move. Try bending it lower down, nearer the solenoid and put the solenoid right at the end (better leverage).
    If the 'nail test' (above) shows that you actually have an electromagnet then you could improve it considerably by using a 'horseshoe' (a U shaped core) rather than just a rod. Two rods, side by side, sitting on an iron bar would do the job. You need not rewind your coil; it can be just on one of the rods.
    Horseshoe magnets (as in all cartoons!) were always used in the past because you could get a much stronger field between the two poles than at just one end. Old steel permanent magnets were rubbish, actually!

    I just thought - that bendy strip could be replaced by a see saw mechanism, which would need much less force to make it move.
  5. Jan 17, 2012 #4
    First check if you actually have an electromagnet by pushing the switch that you made, and see if the solenoid attracts paperclips.

    If it does attract paperclips, then your problem is mechanical in nature: the magnet is not strong enough to attract your L-shaped metal "clicker", but is strong enough to attract paperclips.

    You can try to increase the strength of the magnet, or decrease the strength of the L-shape by making it more bendable.

    A poor man's "clicker" would involve taking a paperclip, straightening the paperclip out, and bending the end to form an L, and jab the end of the paperclip into a styrofoam base. The point is that a paperclip wire is very thin and bendable, so you should have more success.
  6. Jan 17, 2012 #5
    The L shaped clicker should be U shaped and one end should be under the coil and the other end should be closer to the coil.
    Also you might move the body of the clicker farther from the coil so the clicker pulls in easier when the coil in energized.

    Great pictures.
  7. Jan 17, 2012 #6

    jim hardy

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    a "C Clamp" for electromagnet with coil wrapped around its backside would give you a smaller airgap that'd be adjustable...

    you'd have to figure out how to mount it,
    but payoff is the smaller the airgap the better the electromagnet will work.
    Last edited: Jan 17, 2012
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