Demagnetising ferrite magnets

[anchor1]

Is there anyone here who knows how to demagnetise a large ferrite magnet from a speaker.I would like to use it for an experiment.Also if it can be done would passing  north /south magnets over it remagnetise it very much.

Thanks in advance.

[Flux]

It is unlikely that you will manage it without specialist equipment. It is most unlikely that you will be able to get anywhere near the field strength required without resorting to capacitor discharge methods.

You can do it by taking it above its Curie temperature which I seem to remember is about 450 deg C, but I am not sure if there is permanent damage done.

Large neos will partly magnetise ceramics, but not to saturation. To fully magnetise you need about 100,000 amp turns per metre length of magnet so allowing for losses you will need near 10,000 AT to fully saturate it.

If you are trying to produce a multipole pattern on it as Marlec do, you needn't de magnetise it first.

Have fun

Flux

[anchor1]

No I would like to demagnetise it so it can be used as a core for winding coils on for toroidal stator experiment.I have a large bank of capacitors (if my wife will give them back).Will the magnet need be inside a coil.

How many turns and how many joules are required .

Thanks for all the help Flux.

[Flux]

It will be no use as a core for a toroidal winding, you need soft ferrite like the stuff they make transformer cores from. These do not retain magnetism.

Flux

[anchor1]

Yes I was thinking it might remagnetise with the coils on it .I was thinking along the lines of a core that could be fully saturated with the neo's (maybe a thin core)so a variable load at a set rpm wouldn't drop the voltage so much .Then when using a switchmode power supply at different loads the voltage would stay the same eliminating the need for batteries.

I think, then again I could be dreaming.