Lenz's Law aluminum can demo

Demonstrating Lenz's Law on an aluminum pop can, showing how a strong magnetic field passing by an electrically-conducting (but non-magnetic) surface induces mechanical force.

Category:

Education

Tags:

• electronics
• magnetism
• Lenz
• Law
• motor

[catchpen]

I bought a ring that's magnetic and dropped it down stainless metal tubing with the tubing in the middle if the ring i.e. the magnet was on the outside. Unfortunately it didn't slow down, dropped like a rock. Isn't this the same principal or does the magnet have to be in the center?

[BTCInstrumentation]

@catchpen The magnetic field from the magnet must pass perpendicularly through the metal for maximum effect. In your case, the donut magnet probably has North and South poles on its faces, which means a lot of it's flux goes outside the center, not inside. Furthermore, the magnetic flux lines mostly pass parallel through the metal tube, not perpendicular.

[catchpen]

@BTCInstrumentation Thanks for the reply. Hey I got it to work :) , check out my profile for the video sorry for the poor quality. We found a solid bronze rod and it worked. I guess the hollow tubing wasn't a good "conductor".

[BTCInstrumentation]

@catchpen Cool! A solid metal rod has more cross-sectional area for eddy currents than a hollow tube. This makes the most of a non-ideal arrangement.

I've seen a similar experiment where a small spherical magnet was dropped INSIDE a copper tube, and the speed of its fall was greatly inhibited by the effect of Lenz's Law.

[uawwildbob]

good post . lens law still has room for experimentation. are there any nonmagetic metals that are not effected by lens law ?

[BTCInstrumentation]

@uawwildbob Lenz's Law is applicable to ANY conductor of electricity. So long as the metal is electrically conductive (which all metals are), Lenz's Law applies. The effect, of course, is weakened for metals having high specific resistance because that electrical resistance opposes the induced currents.

[TheNeonTide]

wind.

[SpindlyOsprey]

do it in a vacuum chamber with no wind, then I'll believe it

[ChrisGranger]

@Yahuzi Yes, while Lenz's Law is a real effect, this particular demonstration isn't very good for the reason you stated.

[subductionzone]

Nice. You should try another video with the can rotating at high speed on a near frictionless surface and put the magnet over it. The eddy currents should make it slow down much faster than normal. Or hang the can from a string, spin it and have the magnet under it. Again, it should slow down in a much shorter time than a can without a magnet would.

[TxColter]

CLEARLY HE SOLD OUT AND HAS AD PLACEMENTS IN VIDS!!!

/end troll

[Yahuzi]

maybe it it the wind you produce moving your hand back nad forwards, and the wind moves the can? and because the can is really light it doesn't need a lot of wind to move.. dumb idiot -.-

[SpazzyMcGee1337]

Where is a whiteboard when you need one! I need to visualize these fields NAOW!

[william69952]

that is because the aluminium can is not 100% aluminum. it has a small percentage of iron and other magnetic-attracted metals.

[Aleksandr2975]

@Aleksandr2975 Sorry, I did not get it first - if magnet is outside of the tubing, that changes everything.

[Aleksandr2975]

@catchpen I saw some answers... they are not correct. The reasons for no slow down in your case are:

1. Stainless steel has MUCH higher resistense than even mild steel. Sure, the difference stainless steel/copper will be even higher. So the eddy currents will not be sugnificant.

2. Another reason is that these guys are using not just magnets from the store; but really poverful Neoudim magnets