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What Happens When You Drop A Magnet Inside A Copper Tube [video]

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Re: What Happens When You Drop A Magnet Inside A Copper Tube [video]

#61

Post by lutusp »

whatshisface wrote: post #36
sillysaurus2 wrote: post #32

Earlier quoted context omitted.

Could this be used as a kind of elevator tech? I'd love to ride one of these down a gigantic copper tube. It'd be completely impractical, of course, but a whole lot of fun.

The inverse square law of force strength falloff would make it very hard to scale this linearly, that combined with the fact that weight increases with the cube of size means that the magnets involved would have to be incredibly strong. Not impossibly strong mind you, if magnets can hold a hundred ton train car off the ground I am sure they could slow the fall of an elevator. I'd not want to be inside that elevator w…

> The inverse square law of force strength falloff ...

Because there aren't any magnetic monopoles, I believe in ordinary circumstances the relationship is inverse cube of distance. Reference: http://www.newton.dep.anl.gov/askasci/phy05/phy05629.htm

Re: What Happens When You Drop A Magnet Inside A Copper Tube [video]

#62

Post by hnriot »

vecter wrote: post #54
IgorPartola wrote: post #2

Yup, it's pretty cool. This was one of the most impressive demo's my physics professor did in our freshman physics class. The point is that as the magnet is falling through the copper tube it creates an electric current which then creates a magnetic field in the opposite direction of the magnet's movement. In other words, this is the practical application of the Right Hand Rule [1]. Two fun facts about it: first, if…

Technically, this has nothing to do with the Right Hand Rule. That is just a human convention to assign a positive and negative signs to a particular direction. Electromagnetism doesn't care about our silly human notations.

semantics vs syntax - magnets don't have hands obviously, but the metaphor holds just the same.

There is no "technically..." nonsense! It's not a human convention either - it's an anthropomorphic metaphor.

Re: What Happens When You Drop A Magnet Inside A Copper Tube [video]

#64

Post by tall »

laureny wrote: post #37
sillysaurus2 wrote: post #32

Earlier quoted context omitted.

Could this be used as a kind of elevator tech? I'd love to ride one of these down a gigantic copper tube. It'd be completely impractical, of course, but a whole lot of fun.

> It'd be completely impractical, of course, but a whole lot of fun. And at the end of the ride, you want to take a selfie and email it to all your friends but you can't because your phone is fried.

actually not true, modern phones use SSD, and don't really get affected by magnets in the way you might expect.

Re: What Happens When You Drop A Magnet Inside A Copper Tube [video]

#65

Post by IgorPartola »

lutusp wrote: post #61
whatshisface wrote: post #36

Earlier quoted context omitted.

The inverse square law of force strength falloff would make it very hard to scale this linearly, that combined with the fact that weight increases with the cube of size means that the magnets involved would have to be incredibly strong. Not impossibly strong mind you, if magnets can hold a hundred ton train car off the ground I am sure they could slow the fall of an elevator. I'd not want to be inside that elevator w…

> The inverse square law of force strength falloff ... Because there aren't any magnetic monopoles, I believe in ordinary circumstances the relationship is inverse cube of distance. Reference: http://www.newton.dep.anl.gov/askasci/phy05/phy05629.htm

Yup, magnetic field falls off as 1/(distance3). That's why being 5 feet from an NMR magnet is bad news bears, while being 8 feet away is fine (numbers made up, do not test). I remember seeing signs all over the place at our labs at the uni, saying to not enter if you wear a pacemaker or if you are wearing a wrist watch.

Re: What Happens When You Drop A Magnet Inside A Copper Tube [video]

#66

Post by IgorPartola »

rbanffy wrote: post #43
IgorPartola wrote: post #30

Earlier quoted context omitted.

The levitation over a superconductor was the other cool demo that the professor did :).

Lucky kids. When I was in school, the only commercial superconductors were liquid Helium cooled Niobium-Titanium alloys, something not many classrooms could handle. ;-) Luckily, when I got to programming, we already had zeroes and ones. Imagine our predecessors who had to do it with uppercase o's and lowercase l's...

I forget what type we used but it was cooled by liquid nitrogen. That prof. used lots of magnets and superconductors in his research, some cooled by Helium-3. Now that stuff is expensive.

Re: What Happens When You Drop A Magnet Inside A Copper Tube [video]

#67

Post by laureny »

tall wrote: post #64
laureny wrote: post #37

Earlier quoted context omitted.

> It'd be completely impractical, of course, but a whole lot of fun. And at the end of the ride, you want to take a selfie and email it to all your friends but you can't because your phone is fried.

actually not true, modern phones use SSD, and don't really get affected by magnets in the way you might expect.

True, they would only get fried if they used electronic components.

Re: What Happens When You Drop A Magnet Inside A Copper Tube [video]

#68

Post by refurb »

frankus wrote: post #21

Yet another demo: https://www.youtube.com/watch?v=9s9I8OI82Ag

The interesting part is that NMR magnets often have a second magnet within them that creates an opposing force outside of the bore of the NMR (or at least they used to do it that way).

If you notice on the video the yellow chain which keeps ferrous metals away from the instrument isn't really that far away. Also, when he drops the aluminum disc, it actually starts to accelerate after falling only a foot.

Because of the "counter" magnetic field produced, NMRs have a much small/weaker external magnet field that you'd expect.

Re: What Happens When You Drop A Magnet Inside A Copper Tube [video]

#69

Post by smoyer »

JakeStone wrote: post #58
mjcohen wrote: post #55

Earlier quoted context omitted.

Ha! When I was in school, we had to push the electrons around by hand! You kids had it easy!

You guys had electrons? We had to use scotch tape on a bunch of quarks and give them a half spin and then push them. Uphill. Both ways.

I'm declaring a winner here ... the only possible thing that could top that is "through three-foot deep snow".

Re: What Happens When You Drop A Magnet Inside A Copper Tube [video]

#70

Post by robotresearcher »

hnriot wrote: post #62
vecter wrote: post #54

Earlier quoted context omitted.

Technically, this has nothing to do with the Right Hand Rule. That is just a human convention to assign a positive and negative signs to a particular direction. Electromagnetism doesn't care about our silly human notations.

semantics vs syntax - magnets don't have hands obviously, but the metaphor holds just the same. There is no "technically..." nonsense! It's not a human convention either - it's an anthropomorphic metaphor.

Name another animal that uses that convention.
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