If an Eddy current is established within a conductor, will there be more heat generated in high conductivity or low conductivity materials? I can see a case being made for either option. In high-conductivity materials, Eddy currents can be more easily established, leading to more heat being produced overall (after all, in insulating plastic, heat created by Eddy currents is null since no eddy currents are being formed). However, in low-conductivity materials, there is greater resistance, meaning that moving electrons could also create more heat. Which explanation is the correct one? Thanks.
2 Answers
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Both are correct. There are no eddy currents in perfect insulators, while the surface current in a perfect conductor dissipates no energy.
There is energy dissipated at intermediate conductivity. How much depends on geometry. The maximum dissipation tends to occur when the skin depth is comparable to the size of the conductor.
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$\begingroup$ I understand it in the insulating case because the voltage is limited. But what bounds the eddy current in the superconductor case? $\endgroup$– tobaltCommented Oct 26, 2022 at 1:14
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1$\begingroup$ In the superconductor case, the magnetic field interior to the material is zero. Thus, the surface current is exactly the current that cancels the external magnetic field with its own magnetic field within the volume of the material. $\endgroup$ Commented Oct 26, 2022 at 1:51
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In a given situation where the dimensions of the material, rate of change of magnetic field, etc are the same the induced emf is the same irrespective of the type of the material.
Given that power $= \text{emf}\,^2/\text{resistance}$, the smaller the resistance the greater is the power dissipated.
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$\begingroup$ Except that the eddy current makes an EMF, too. $\endgroup$ Commented Oct 26, 2022 at 1:48