Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

digg.com

Post reply on HN
Print view View original

121–125 of 125 posts

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

#121

Post by exhilaration »

hurowits wrote: post #113
taliesinb wrote: post #20

Earlier quoted context omitted.

You can also think of it as magnetic flux lines encountering "drag" as they pass through conductors. The limiting behavior of this view is in type II superconductors, which entirely "pin" flux lines -- they present an effectively infinite resistance to the movement of flux lines. That's why a magnet levitates over such a superconductor. [1] You can even image these "vortices" directly [2] [1] http://en.wikipedia.org/…

You might wanna take a look at this video: http://www.youtube.com/watch?v=VyOtIsnG71U

Incredible. For anyone watching, make sure you at least go past 2:20 - that's when they pull out the magnetic rail.

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

#122

Post by marcosdumay »

e12e wrote: post #96
aaronsnoswell wrote: post #26

Earlier quoted context omitted.

The effect works just fine with thinner tubes and smaller magnets - I've done it using 15mm 'plumbing' copper pipes.

Should work with a paper tube and copper wire as well? [edit: not saying that would be cheaper and/or easier, just that it should be possible...] [edit2: A stripped wire, that is - not one with insulation -- which would be more suitable for making a spool]

If you close the wire (join the 2 points) you should get something, but certainly not as strong.

You can try that with aluminium if cooper is too hard to get. You'll probably get better results.

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

#123

Post by cLeEOGPw »

ansgri wrote: post #112
cLeEOGPw wrote: post #107

Wonder for how long the magnet needs to fall until it is completely demagnetized.

Why should it. The energy is supplied by gravity.

As magnet falls, it is slowed down, this drag is created because magnetic forces are resisting gravity. So after some time, magnet loses that force, I just wonder how long does it take. It can't fall slowly like that forever.

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

#124

Post by robotresearcher »

nrivadeneira wrote: post #79
robotresearcher wrote: post #70

Earlier quoted context omitted.

Name another animal that uses that convention.

The point is that it's not a convention - it's a metaphor, as hnriot pointed out.

It's not a metaphor.

http://en.wikipedia.org/wiki/Metaphor

No one is comparing or likening charge to some other thing. We simply give opposing charge "directions" a name. Everyone uses the name. It's a convention.

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

#125

Post by nrivadeneira »

robotresearcher wrote: post #124
nrivadeneira wrote: post #79

Earlier quoted context omitted.

The point is that it's not a convention - it's a metaphor, as hnriot pointed out.

It's not a metaphor. http://en.wikipedia.org/wiki/Metaphor No one is comparing or likening charge to some other thing. We simply give opposing charge "directions" a name. Everyone uses the name. It's a convention.

The comparison that is being made is the direction your thumb points when your fingers wrap in a particular direction. It's not merely giving it a name - it's specifically likening the vector to the relative orientation of your fingers. That's why the comparison is memorable. If it were merely a name with nothing that it is compared to, it would not be memorable nor helpful.
Post reply on HN