Discussion in 'Supporting Physics' started by Technician Q, Jan 16, 2020.
We have a rather large collection of weak bar magnets. What's the best way to strengthen them?
We've got a 'magnetising and demagnetising solenoid' (like this https://www.philipharris.co.uk/prod...s/magnetising-and-demagnetising-coil/b8h26319 , but about 50 years older !) which I believe is designed for the purpose. I haven't actually used it yet, I discovered it in a cupboard last week, but I'm planning to give it a try soon and I'll report back !
We have a fairly ancient one called "The REMAGNETIZER" (their spelling) and it works very well. Also quite a calming, routine task! "North Pole in, flip magnet over. South pole in, flip magnet out". Ah the simple pleasures of technician life (if one has the time)
I have a magnetising box, must have a pretty strong permanent magnet in it. I just check the polarity of the bar magnet with my trusty pole checker and put the bar magnet on the box taking care not to trap any part of me between the two. Results are presumably instant but I just change the bar magnets over whenever I remember. No elecktrickery required. I do use a solenoid for degaussing though.
buy new ones.
Never seen coloured magnadurs before, assuming that's what ceramic magnet means. They are too brittle to stand up to the treatment our alnicos get, though it is hard to find decent alnicos at a sensible price.
they are in plastic
Sounds interesting, magnadurs are usually poled on the face, so they are very unusual. Are they tough then? Might have to try them.
apart from the ones that are pinched no problems and at 60p i might have to be easier on the teachers...
We have one of those - I'll have to have a play.
I found a second hand major magnet for £80 on eBay and it has done the job of re-magnetising perfectly, plus it can be used for other practicals. Although the price for a new one is around £150....
Pretty sure I've got one of them, how do you use it to re-magnetise another magnet ? Thanks
Be v careful with the Major not to pinch fingers between as you re-magnetise - maybe wear thick gloves. And do it in an area where magnetism will not create an issue (do not do around your tech or phone, cards, pacemaker, etc!). Take the safety cap off the major magnet and put one you want to re-magnetise to the opposite pole. Touch north to south then flip around and touch south to north. Do this few times until you find the magnetism returns through trials with objects you expect it to pick up easily.
Many moons ago, I built a mains powered remagnetiser. Very easy construction and should be less than the cost of a set of magnets. All except the coil was enclosed and it had a big sign on it explaining that it would happily kill you if abused. Made a very satisfying "thunk" when it was triggered.
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