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Do we require less power in the superconducting (cryogenically Cooled) electromagnet than the resistive type electromagnet?

If you have any figures or the voltage and current graph for both magnets, please share those stats.

If you know about any research paper on the comparison of the electromagnet then please let me know

Smit Fefar
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This is not a straightforward comparison because typically persistent superconducting magnets are 'charged' initially and energy is only consumed to keep them cold (perhaps with a cryocooler), otherwise they act like permanent magnets once charged. If liquid helium is free you can just keep topping up the cryostat. Resistive magnets require power (and perhaps cooling) for as long the field is needed.

An MRI magnet might have stored energy in the field of a couple megajoules. While that's a fair bit if it gets released suddenly, it's only about 0.6kWh so pennies worth of electricity.

So it really depends on the how strong the required field is, and other characteristics of the use case.

Spehro Pefhany
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Identical currents in identical physical configurations will produce identical magnetic fields. That is, if you have 1 amp flowing through a copper coil of a particular shape, and one amp flowing through an aluminum coil with the exact same shape, they will produce the same magnetic field.

However, because aluminum has a higher resistivity than copper, the voltage that is needed to maintain 1 amp through the aluminum coil will be greater than the voltage needed to maintain 1 amp through the copper coil. As a result, the copper coil will generate less heat than the aluminum coil. This heat is not at all useful for producing the magnetic field. From the point of view of using the coil as an electromagnet, the heat produced is simply unavoidable waste of power.

How much voltage does it take to maintain 1 amp in a superconductive ring? Actually, none. It takes voltage to ramp up the current in a superconductor, but none to maintain that current. See the London Equations. (The above statement will be true provided the magnetic field created by the superconductor is not so great that it "turns off" the superconductivity.)

So, an electromagnet that has a superconducting coil will be much more efficient than an equivalent coil with resistance. If the superconducting coil forms a closed circuit, the coil will essentially form a permanent magnet, not requiring any power to maintain its magnetic field.

Math Keeps Me Busy
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  • Being a pedant, I have to ask how the power requirements for creating the cryogenic environment figure into the overall efficiency of a superconducting coil /s – Peter M May 14 '23 at 18:07
  • @PeterM The cost of maintaining a superconductor at a low temperature depends upon the thermal resistance between the superconductor and the ambient environment. The superconducting magnets in, say research particle accelerators, are, AFAIK, quite efficient. Much more so than conventional electromagnets would be. But the equipment is obviously very complex and costly, and doesn't lend it self to use on a crane in a steel scrap-yard. Nor obviously in a small solenoid valve, unless perhaps if the solenoid valve is controlling the flow of liquid helium. :-) – Math Keeps Me Busy May 14 '23 at 18:18
  • Hmm .. and how much does the helium cost? lol I'm saying this mostly in jest, but for an apples to apples comparison you do need to take in to account everything needed to create the equal magnetic fields. Which raise the question for me - could you even produce the same field strength of say an MRI machine with a resistive electromagnet? My gut feeling is probably no you can't. – Peter M May 14 '23 at 18:27