Residual electromagnet magnetism

In summary, residual magnetism in an electromagnet is an undesirable side effect that may cause the magnet to still hold onto particles when it should let go. It is not considered free energy as it may only slightly reduce the power needed to magnetize the magnet in the future. Moving the magnet through a coil could potentially generate electricity, but this would not be considered free energy either. Overall, there is no practical use for residual magnetism in an electromagnet as it is too small to be of any alternate benefit.
  • #1
bobbobwhite
51
0
Have always wondered this so maybe I can get an answer here: when a large industrial electromagnet is switched off and the electricity-produced magnetism ceases, is there a small amount of residual magnetism in the uncharged electro-magnet? If so, does it dissipate according to a established formula? If it exists, it is essentially free energy at that point, so could it be used for an alternate and lesser purpose before it dissipates thus saving the energy needed to produce it for this alternate use?

I imagine the real question here is: if it exists, does it have any practical use before it dissipates? Or, if it exists, is it too small an amount to be of any alternate benefit?

Thanks for all informed answers.
 
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  • #2
Residual magnetism in an electromagnet is an undesirable side effect.
It may mean that the magnet will still hold small particles like iron dust when it should let go of everything.

I don't think you can call it free energy except that it may take slightly less power to magnetize the magnet next time. However, electromagnets usually get the same power every time they are turned on, so this slight advantage is not used.

Mostly it is a very small effect because very low carbon iron is used to make the electromagnet.
 
  • #3
You can't get energy out of a static magnetic field, so even with a high-remanence core (that's a fancy term that means a residual magnetic field is left after the coil is de-energized) you can't get any "free energy". As with all permanent magnets, you could move it through a coil to generate electricity--this is, after all, how all generators work--but that energy isn't free; the energy ultimately comes from whatever it is you use to move the magnet, be it coal, nuclear, gasoline or you.
 
  • #4
Thanks for the responses. In considering all forms of energy conservation, I sometimes ponder any possible way to save wasted energy no matter how small or inefficient the savings may be. One day I may think of one that is practical but not this time, I must assume.
 

FAQ: Residual electromagnet magnetism

What is residual electromagnetism?

Residual electromagnetism is the presence of a magnetic field in a material even after the external magnetic field has been removed.

How is residual electromagnetism formed?

Residual electromagnetism is formed when a material is exposed to a strong external magnetic field, causing the atoms in the material to align and create a magnetic field. This alignment remains even after the external field is removed.

What are some common materials that exhibit residual electromagnetism?

Iron, nickel, and cobalt are common materials that exhibit residual electromagnetism. Permanent magnets, such as those used in speakers and motors, also have residual electromagnetism.

What are the practical applications of residual electromagnetism?

Residual electromagnetism is used in a variety of applications, such as in magnetic storage devices (like hard drives), magnetic sensors, and magnetic levitation systems. It is also essential in creating permanent magnets for various industrial and consumer products.

How can residual electromagnetism be reduced or eliminated?

In most cases, residual electromagnetism cannot be completely eliminated, but it can be reduced by using materials with lower magnetic permeability, applying an opposite magnetic field to cancel out the residual field, or heating the material above its Curie temperature to disrupt the alignment of atoms.

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