Does using permanent magnets to induce current weakens them?

[Maxc13]

Does induction weaken permanent magnets? Lets imagine a stationary permanent magnet and a stationary coil, lets imagine that through a procedure, doesn't really matter how, we direct the magnetic field of a pemanent magnet in a way to make it reach the stationary coil in a pulsatile way, thus exposing the coil to a time varying magnetic field. Normally this should induce current in it, as it does in DC motors/gen.
In all the cases I know where permanent magnets are used to induce current they never seem to weaken (for decades) and I was wounderng why? Could you explain me what will happen in this example and if the PM could weaken with time.

 

[MagMike]

No, induction does not weaken permanent magnets. There is a reason why they are called permanent magnets.

Some magnets will decay over time, usually due to extreme circumstances like temperature, corrosion, strong opposing magnetic fields etc.

 

[IRstuff]

Typically, permanent magnets are magnetized while still molten, or with extremely high fields, which physically alters the alignment of the magnetic domains within the material. Once the material cools down, the magnetic domains are permanently aligned together, and only extremely high fields or temperature can demagnetize the material.

The induced field from the coil would be too low to perturb the PM. However, if you drive the coil directly and generate a sufficiently large field, you might possibly weaken the PM.

TTFN
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[Maxc13]

Thank you for your replies they were very helpful

 

[EdStainless]

If you look at demagnetization curves from testing permanent magnets you will see how well they resist demagnetization. If you only expose a magnet to a small demag field then it will recoil back to its full strength. Remember, any time that a magnet is working (even just stuck to the fridg) it is trying to be demagnetized. It is the magnet resisting this that allows us to get work.
It is possible for magnets to partially demagnetize each other, but it would be a poorly designed system.
If magnets are going to be exposed to an external field it is important to check the system design to assure that you don't lower the strength of the magnet over time.

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