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Calculating the magnetic field inside a closed loop of wire

  • Thread starter aftershock
  • Start date
  • #1
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Homework Statement



I basically have a closed loop of wire with a current flowing through it clockwise. I need to determine the magnetic field in the center, along the z-axis.

Homework Equations



Ampere's Law and Biot-Savart Law

The Attempt at a Solution



Using Biot-Savart Law I actually pretty easily calculated the field and it was correct. (sorry for not typing out formulas but the math symbols seem to be giving me trouble and I don't think I need to).

But if I use Ampere's law, then as soon as I place an amperean loop in the middle of the wire the I enclosed is 0, leading me to believe there should be no magnetic field within the wire. How am I using Ampere's law wrong?
 

Answers and Replies

  • #2
1,254
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What direction is the magnetic field going at the center of the wire-loop?
And just because there's no current enclosed doesn't mean there's no magnetic field.... just no net field along (and in the direction of) the amperian loop.
 

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