A Permanent Magnet That Turns On and Off

hey everyone today we're going to be seeing if it's possible to turn off or block a permanent magnetic field so it would be nice if you got something stuck to a giant neodymium magnet like this one that you can actually remove it if you could just turn off the magnet now if it were an electromagnet you could easily just turn off the current going through it and it would no longer produce a magnetic field but with permanent magnets like this neodymium magnet here it's not so easy to turn it off but it actually can be done so let me show you two ways that you can turn off a magnet or block its magnetic field and then i'll show you the true way that you can actually turn a magnet off and on again so let's start off with a pretty decent size cylindrical shape neodymium magnet this magnet is pretty strong by itself so let's see if we can just block it by putting some metal over it now we're going to be able to see the magnetic field by putting this special magnetic paper in front of it that lets us see the magnetic field so first let's take the sheet of non-ferromagnetic metal here so you can see the magnet does not stick to it but you can see the magnetic field easily penetrates this so i wasn't able to block the magnetic field here but let's try to use a piece of steel now so it's going to easily stick to this but even with the piece of steel it's not completely blocking the magnetic field you can see it right behind here it's pretty cool it looks like we have x-ray vision through this steel here you can see the magnet behind it but if we get a thicker piece of steel and stick our magnet to it now we can't see anything so we didn't actually block the magnetic field here what we actually did is create an easier path for the magnetic field lines to go through so the still provides an easier path for the magnetic flux to go through than the air so that's why it's able to block it although it's not really blocking it it's just creating basically a short circuit path for the flux to go through so it doesn't show up in the air on the outside of it so when we try to stick anything to it it doesn't stick [Music] so we were able to shield the air around it from this magnetic field by using a thick piece of steel like this but eventually this steel will become saturated if i apply a stronger magnet to it this still will become so saturated that it will no longer be able to contain any more magnetic flux and so it'll just penetrate into the air again around it so let me show you with my giant neodymium magnet oh [Music] okay all right so now i have my magnet stuck to the back here even though it's through a few inches of acrylic it's still on there very tight but now you can obviously tell that some magnetic flux still goes through the steel so this still became saturated and is letting the magnetic flux go through it and penetrate the air again so the bigger the magnet the more still you need to block that magnetic field now one way you could turn off the magnet but not turn it back on is by heating it up for example if i just stick a little neodymium magnet to this steel plate here now if i heat this magnet past its curie temperature which is the point at which the magnet loses its permanent magnetic properties oh no longer sticks to it at all or anything that's still so i basically destroyed this magnet here so at around 600 kelvin in these neodymium magnets all the magnetic moments that were initially pointed in the same direction got enough thermal motion that they weren't all pointing the same direction anymore they became so disordered that it's no longer a magnet but the problem with turning a magnet off like this is you can only turn it off you have to re-magnetize it somehow to turn it back on so when we heat the magnet past its curie temperature we can turn it off or when we try to block it with thick steel we can turn it off but in both of these methods we can't really turn it off and on but what if there is a way to intelligently turn off and on permanent magnets well it turns out there is a way to do this with something called a mag square so notice on here it has an on off switch this is a permanent magnet this is not an electromagnet so right now it's on and it can easily pick up these still pieces of metal here but then watch what happens when i turn it off they just drop off like nothing and it can't even come close to picking them up again it's completely non-magnetic now but turn it back on it just sucks them up here's a huge iron nail here turn it on and i literally cannot pull this off it is locked on there but luckily i can just turn it off and it drops off like nothing and then it's not attracted to it at all you can use it to pick up a piece of metal and it holds it really solidly but then when you want to release it you just turn it off and it drops off i mean watch how sensitive this is i have a tiny little staple here and look how it can't pick this up at all when it's off it's completely blocked the magnetic field there's absolutely no magnetic field here not even enough to pick up a staple then turn it on and it just sucks it up so how does this work how is this turning a permanent magnet off and on again okay so let me show you how this works here i have a piece of steel behind this paper here and so you can see that i have two neodymium magnets here that individually stick to the still now i've marked the north end of these magnets here so you can tell which side is pointed which way now i can put both of the south sides of the magnet on a steel coin here and it will still stick to the steel plate behind it but if i change the direction of one of these magnets so that one of them is now north side facing up and the other one is south side facing up notice that it doesn't stick anymore so now if i were just to say that this steel coin where my magnet you can see that it's not magnetic right now but then if i just flip the direction of one of these magnets then it becomes magnetic so if you didn't know what was inside the black box here you would say that i was turning this magnet off and on when in reality all i was doing is switching the direction of one of these permanent magnets inside of it so why is this happening why is this so efficient in blocking the magnetic flux well the reason is remember that the magnetic field lines are always going to try to go from the north pole to the south pole or vice versa so they're going to want to loop around in a circle like this but if you put a piece of steel there then the steel is going to want to give it a shortcut to go from the north pole to the south pole so when i have them face the same direction they're basically like the same piece of magnet here so the magnetic flux lines are just going to go from this side around to this side so when i put another piece of steel close to it it's easily attracted to it but then if i switch one of these around now the magnetic field lines they just want to go in a short little circle right there because it just wants to go from north to south or south to north so they just want to form this little short circuit there so they don't really want to escape from the steel plate here to go into this other one below it so it's not really attracted to it at all so the way you turn it off and on is just by manipulating the magnetic field so they always want to take this shorter path and they don't want to go through something outside of it and that's actually exactly what's going on inside of here except just to a more precise level and so if you can get two of these on top of each other and you can just rotate them 180 degrees then you're basically doing the same thing i was doing by flipping one of these 180 degrees except now that it's a cylinder you can completely surround it by still on either side and then you can completely block the magnetic field and make it direct it so it goes from one side to the other and thanks again for watching another episode of the action lab i hope you liked it i hope you learned something if you have any comments or questions let me know in the comments section and check out the actionlab.com to see the action lab experiment boxes or you can check out the link in my description to see my experiment book that's now for sale on amazon and if you haven't subscribed yet remember to hit the subscribe button and hit the bell so you can be notified when i release my latest videos and thanks for watching and i'll see you next time you

Channel: The Action Lab

Views: 1,113,465

Rating: 4.9360909 out of 5

Keywords: magnet switch, off and on magnet, the action lab, giant neodymium magnet, monster magnet

Id: PMma3OJUHhs

Length: 9min 54sec (594 seconds)

Published: Tue Dec 01 2020