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Old 01-10-2019, 08:56 AM   #4480 (permalink)
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You do not need any energy to maintain the magnetic field in an electromagnet!
The only power an electromagnet consumes is what's needed to overcome the resistance of the conductor.

If you do not have resistance, like when the coil is cooled down until it is superconductive, you could short the ends and the magnetic field would be like a permanent magnet.

If you want to change the strength of the magnetic field then you need to change the strength of the current, which requires of provides power.

If there was a way to change the strength of a magnetic field of a permanent magnet, that would of course require power, just like it does with an electromagnet.

Bear in mind that introducing a magnetic field influences all charged moving particles (like all electrons in an atom).
If you drop a strong magnet down on a conductive plate that will cause a current circling round in the material, forming an electromagnet with opposing flux, slowing down the approach of the magnet.
If that plate is superconductive then the magnet will come to a standstill, hovering above the plate, kept in balance by the opposing magnetic field it created in the plate by approaching it.

The plate material is de facto an electromagnet, 'powered' by the intrusion of the magnetic field of the small magnet above. It does not need energy to maintain its field; rather, the longer energy (heat) is kept away, the longer it persists!
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Last edited by RedDevil; 01-10-2019 at 09:16 AM..
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