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I'm not sure if this is the right place to be asking this question, so close it if it's not, but I need help on a physics project. My current project is a ring launcher (Elihu Thomson Apparatus). I spent the last week winding 4,893 coils of 30 AWG magnet wire around a steel pipe which I filled with some small diameter metal rods (I'm not sure of the material, but it seems to be fairly ferromagnetic). On the steel pipe right next to the coil is a 1 inch copper pipe (the two are insulated from each other) free to move. When I hook the coil up to the wall, I get a nice changing magnetic field (according to the Hal probes in my phone) but nothing else. I'm not following any particular tutorial, but I've seen similar setups around the web that work and launch the ring. Any ideas on where to go? I can take pictures if those would be helpful. Just tell me what you would like to see.

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    \$\begingroup\$ How about a link to what you are trying to do? A ring launcher sounds like something potentially painful attached to a chair waiting for the unsuspecting to sit down; rather like a whoopee cushion but with far more attitude. \$\endgroup\$
    – Andy aka
    Commented Jul 26, 2014 at 17:27

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A ferromagnetic ring will sit and vibrate at the AC cycle rate. Pulsed DC is likely what you need. Typically "washer launchers" are a big bank of capacitors with voltages in the kilo (kill-you) range that are triggered to dump and "fling the ring". If you do not have the equipment to handle these measurement tasks, that is where you need to start. Get the test equipment.

For non-ferromagnetic, but conductive, rings, you sound like you're on the right track.

There is a physics youtube channel that has a "launcher" of the sorts that is sounds like you are talking about. They use room temperature [Al] and test, then the same ring Liquid[N] cooled.

Keep in mind the device in this video uses UK line voltage.

The Electric Cannon

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Oddly enough, I think you spent way too much time on your coil. I don't know the exact core material, but a rough calculation using a permeability of 50 suggests that your coil has an inductance of ~ 10 Henries, and you used about 2000 feet of wire, so your resistance is about 200 ohms. The problem is that this is very slow to respond to a change in voltage, and the average current in the coil is only going to be about 50 mA.

While it may be painful to contemplate, you might try making a coil out of 20 ga wire instead. the same size coil will have ~ 20 ohms resistance and .1 H inductance. At least, with only ~ 500 turns, it won't take as long to wind.

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