Screwdriver demagnetizer

I think you have to shake the screwdriver really really fast. ;)

The main idea is to make a few laps around the B-H loop with successively smaller fields until the remanent field is small. Rate is not important but going on both sides of B is.

I am guessing, but think that the field diminishes and reverses in each of the steps in demagnetizing. But the more I think about it, I am not sure the field has to reverse.

If no one checks their demagnetiser and lets us know if the field reverses, I will do some checks and see if the field has to reverse.

Dan

To demagnetise, you essentially attempt to magnetise the screwdriver across its width - the permanent magnets in the demagnetiser are arranged so the field goes across the screwdriver, but that's too short a distance for steel to hold a permanent magnet. I don't know the technical term, but basically you can't make a short steel magnet, the poles will sort of collapse. Someone who knows better will doubtless be along soon.

To magnetise, the field is orientated along the length of the screwdriver.

They work quite well FSVO quite.

Cheers

On a sunny day (Mon, 1 Feb 2016 17:23:44 -0500) it happened mixed nuts wrote in :

That is how audio tape recorders work(ed), the RF bias.

Well the field has to reverse... (at least in my model of how it works.) If someone has one perhaps they can determine the field direction in the thing...

George H.

thing...

Maybe. Visualize a B-H curve for a screwdriver. It is not real square loo p , but not real soft magnetic either. So you go up on the curve and when you remove the external field, you go back to lower point. Then you do th at again but not so far up, and again relax. And then one more time.

Reversing the field would be better, but I am not sure it is required.

Dan