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Calculating current through solenoid?

  1. Feb 24, 2015 #1
    Not for a class or anything, just out of curiosity, how would you calculate the current in a solenoid, not given a magnetic field, but just using a bar magnet? I know it will just be some form of Faraday's law. E=N(dphi/dt). Maybe not. I'm imagining all I'm really missing is how to calculate the magnetic field of the magnet. Thanks.
     
  2. jcsd
  3. Feb 24, 2015 #2
    Take the solenoid and connect a voltmeter or multimeter across it. Move the barmagnet towards the solenoid and there should be a deflection in the voltmeter because ##\phi## changes when you keep moving the barmagnet.
    or as you know, the bar magnet is also like a solenoid. The expression for magneticfield for barmagnet along axis is $$B=\frac{\mu_0}{4\pi}\frac{2m}{r^3}$$
     
  4. Feb 24, 2015 #3
    So, just a little clarification, I did a little research online, is M the magnetic strength of each pole and r, I take it is the distance?

    Thanks btw.
     
  5. Feb 24, 2015 #4
    M is the magnetic fipole moment. Here, ##m=n(2L)I(\pi a^2)##
    L is the length from midpoint to one end and 'a' is the radius. 'r' is the distance from midpoint to any point along the axis.
     
  6. Feb 24, 2015 #5
    Awesome. Thank you
     
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