Frequency and Magnetic Field

Author Topic: Frequency and Magnetic Field (Read 2240 times)

Mookie	Frequency and Magnetic Field « on: 2011-06-28, 03:45:03 »
Jr. Member Posts: 63	Increased / decreased current to a coil / electromagnet has a direct proportional affect on the strength of the magnetic field. What about frequency ? In North America, household current is delivered at 60 Hz, in Europe at 50 Hz. What direct affect does higher / lower frequency have on the magnetic field of a coil / electromagnet ? Mookie

exnihiloest

Re: Frequency and Magnetic Field « Reply #1 on: 2011-06-28, 10:13:29 »

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Posts: 1504

Quote from: Mookie on 2011-06-28, 03:45:03

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What direct affect does higher / lower frequency have on the magnetic field of a coil / electromagnet ?
...

From an electrical viewpoint:
A magnetic field through a circuit induces an emf proportional to dphi/dt which is the rate of the varying magnetic flux, it follows that higher the frequency, higher the ~~voltage~~ emf. There is no consequence on the energy, except for practical considerations about coupling, impedances, losses...

From a physics viewpoint:
Energy density in a magnetic field is B²/(2*µ). It depends only on the field intensity squared, not on the frequency.
The frequency F determines only the energy quanta E=h*F (h= Planck's constant) building the field, i.e. photons (EM waves) or virtual photons (static and near fields). Therefore same energy density at lower frequency implies only more photons/virtual photons than at higher frequency.

« Last Edit: 2011-09-22, 10:43:18 by exnihiloest »