I'm thinking of doing an experiment based on the question. But I have no idea if it will work. I've tried finding things on the internet, but they all talk about the diameter of the wire, not the coil. I think it might work(as in there will be noticeable time differences) but like theoretically what would be the explanation? Because, assuming the length of the coil is the same, the coil with the bigger diameter will use more wire, so idk if that will affect the time taken as well.

edit: I'm thinking of doing 6 different diameters(cm):5,6,7,8,9,10

edit 2: I'm now wondering if it will even work if I use a wire? Because, I've seen people demonstrating this with thick copper pipes or thick aluminium sheets, but never a coil of wire. There must be a reason for that right?

edit 3: I could also use aluminium foil to do the experiment if the coil doesn't work

  • $\begingroup$ Please, let's not have posts look like revision histories. $\endgroup$
    – Urb
    Oct 18, 2020 at 17:23
  • $\begingroup$ Questions: Is the magnet dropped through the coil? Are the turns of wire insulated (perhaps with a varnish)? Are the wires from the two ends of the coil shorted together? How long is the coil? $\endgroup$
    – R.W. Bird
    Oct 18, 2020 at 19:06
  • $\begingroup$ yes the magnet is dropped through the coil. The wires are not insulated. The 2 ends are not shorted together, I think (I'm not sure what that means). The coil can be as long as it needs to be. $\endgroup$
    – prata
    Oct 18, 2020 at 23:21

1 Answer 1


The changing magnetic field from a moving magnet can induce a pulse of current in the coil. The magnetic field from the current can act back on the magnet. For a magnet of given strength and size the interaction with the coil should decrease as the coil increases in diameter (while keeping the number of turns constant).


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