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What is the physical relationship between current (I) and magnetic flux density (B)?

Question #101993. Asked by jonnowales.

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looney_tunes star
Answer has 8 votes
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looney_tunes star
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3287 replies avatar

Answer has 8 votes.

Currently voted the best answer.

Referring to the magnetic field produced by an electric current (only one of the possible ways of interpreting this question), the Biot-Savart law provides a non-relativistic approximation: "In the special case of a constant, uniform current I, the magnetic field B is

B = K_m I int frac{dmathbf l imes mathbf{hat r}}{r^2} "

The mathematical symbols don't copy nicely! The magnetic flux density is proportional to the steady current, but varies as you move away from the conductor in whoch the current flows.

link https://en.wikipedia.org/wiki/Biot-Savart_law

If you refer to the current induced when a conductor moves through a magnetic field, then the induced emf is proportional to the rate of change of the magentic flux with respect to time (Faraday's Law); assuming an ohmic conductor, the current will be proportional to the emf; if the magnetic field is uniform, magnetic flux is proportional to magnetic flux density so I is proportional to dB/dt. (This is a vastly-simplified situation, but the mathematical symbols needed to show a more accurate answer are hideous when copied here!)

link https://en.wikipedia.org/wiki/Electromagnetic_induction

Dec 29 2008, 6:08 PM
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