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Solenoid + Transformer + Current buildup interval

  1. Mar 11, 2012 #1
    I decided to make a couple solenoids. Not too many loops on them though as I need higher gauge wire. After getting that I put one in the other and in that a core of metal that had some iron in it. I tried inducing a bit of current in the outer winding by driving DC current through the inner coil - I also tried having the reverse done. Now I know you need AC current, but I thought that I would at least get a pulse of an electric potential difference when first sending current through. While I did, it was extremely small.

    I then made some calculations and it seemed to show what I was getting was to be expected. I need a much greater coil density - especially the coil to be induced (I am wanting to up the voltage.)

    But my question lies with the time at which it takes for the driven current to reach maximum, and thus the B field. When calculating I got about 31.93 ms. I know I did not have a lot of precision with obtained measurements, but could this be a plausible time interval? I know that it wouldn't make sense to say that it is instantaneous for many reasons, though one being that that would mean the magnetic field is created instantaneously and thus infinite induced emf on the outer coil - thats not so.

    Last edited: Mar 11, 2012
  2. jcsd
  3. Mar 11, 2012 #2


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    Staff: Mentor

    Hi Sefrez. I'd regard that as a feasible time. :smile: With only a few dozen turns the inductance will be low. Instead of looking for the induced pulse when you connect the battery, look for it when you disconnect the battery. dI/dt is likely to be much greater and hence the induced voltage greater. You can interrupt the current sharply by breaking apart a connection. To make many rapid connect/disconnect actions, run one of the wires along the teeth of a hacksaw blade incorporated into your current's path. :tongue2:
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