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Homework Help: Solenoid current physics problem

  1. Jul 25, 2006 #1
    A solenoid has a field of 1.5 T when the current is flowing in it. Its cross-sectional area is 0.30m^2. Another solenoid with 150 turns and a resistance of 20 ohms is wound tightly around the original solenoid so that both solenoids have the same cross-sectional area. The current in the first solenoid is reduced to zero uniformly over 0.5s. What current flows in the second solenoid during this time? Can some one help me with this question I am completely lost!
  2. jcsd
  3. Jul 25, 2006 #2
    Just apply Faraday's law to find the induced voltage, then Ohm's law to find the current. You can ignore self-inductance (I think) because the length of the solenoid is unknown.
  4. Jul 26, 2006 #3


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    You would just use V=dF/dt, where F is the flux. This should be easy (uniform change means just divide change in flux by change in time). Once you have the voltage and the resistance, I hope you can find the current
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