字幕列表 影片播放 列印英文字幕 I've got two bits of metal. This is an aluminium cylinder. So long on a similar cylinder of near Damien on. These two are gonna pass through a copper cylinder. Can you see down it? Yeah, right away. Through. Now then. This is the cup, too, with an aluminium soda, and I'm gonna put it in there and no force will be exerted on this, apart from gravity. So doing a quick some that's gonna fall down in about 1/3 of a second. Just about court it, dear. So that's how quickly the aluminium fools Now I'm going to put the near Damien in the abdomen is one of these new magnets. It's incredibly powerful. 234 After about a count of four, slow counter for maybe four seconds, it comes out. So this is more than 10 times as long as the aluminium. As this magnet falls down, say, gets to there. Then it's inducing currents which will be coming around this way. And these currents coming around this way will induce a magnetic field pushing in the opposite direction. So as this comes down this imagine a magnet that I've got is going to be pushing in the other direction, holding it up, holding it up, stopping it from accelerating. And it gets to a finite for lost E, which it travels all the way down the cylinder. I'm gonna put the copper tube inside an aluminium cylinder. I'm gonna put the near Damien magnet in. And the question is, what's gonna happen as the near Damien magnet falls through? That a little aluminum cylinder? Is it gonna stay still is gonna be pulled up? Is it gonna move it all or does it just say stationary at first sight? You might think nothing can permeate through this copper cylinder. Nothing could happen it all. It might shield it, but this is happening very, very slowly. So I'm now gonna drop it and you can see what happens. And you see, as the magnet went past this, it pushed it down. Even though it wasn't touching anything, it pushed it down. If I do that again in case that wasn't so good. All right. This isn't about magnetic attraction as you would attract a paper clip This if I move this very slowly, the aluminium does not pull towards the new demon magnet. This only works when the magnetic field that comes out of here thread through this hole. If I put it on the side, nothing happens. But if it thread through the hole, then it will move. If I move the magnet down to here, the magnetic field is not threading through this hole in any appreciable amount. So put it there and it doesn't attract a tool if I put it there, then the magnetic field through thread through the hole. But if I move it very, very slowly in words, nothing much happens. But if I move it out quickly without touching the sides, the magnetic field is changing rapidly. The part that threading through that hole that's inducing a current in the outside, they're attracting each other. That's weird, because this is, without anything happening, a force between these two, which depends upon the speed at which I pulled right away. What do you seeing that? That's nothing. So why don't we drop something through it? Just make sure it's a thing.