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Hi youtubers! In a previous video I had some fun with eddy currents.
As a response to this video I got a message from mikefromspace where he
basically told me that I should be aware off the poles on the magnets
for better results. I was a little skeptical because for any practical
purposes the south and north poles on a single magnet are equally strong.
But I like experimenting with magnets so let's test it.
First I mark the poles on the magnet using a compass.
Check the video link in the description for more details on how to do this.
And now - let's try it using the 90 degrees drop test.
First five times with the south pole against the copper.
Let's see how many times it makes it without falling off.
Fail...
Fail...
Oh come on!
Fail...
Nope... that was quite pathetic. Let's try it with the north pole against the
copper instead.
Oh yeah!
So close.
Perfect.
OK.
Ooooohhhgghhhh...
So it does look like the north pole is much better for this test.
I did of course perform all tests far away from my huge magnets that
have quite a dramatic effect on north and south in parts of my house
but I couldn't remove the Earth's own magnetic field so maybe this is the reason for
the results?
I quickly aligned the copper bar north/south
and tried on all four sides
but it still was the north pole that performed best on all sides.
Shouldn't we expect a big difference on the copper bar's north and south sides if it
is the Earth's magnetic field that makes the difference?
Well - there isn't an obvious difference
but then I remembered a trick I came across when making the video about
determining the poles of a magnet.
If you drop a neodymium magnet it will - where I live -
have a tendency to end up with the south pole upwards.
To explain this we need to look at our world on a bigger scale.
Based on my videos view analyzer chances are that you're sitting
somewhere here in North America
but I live over here in a tiny country called Denmark.
Let me just zoom in. It is that tiny peninsula right there.
If I point on Denmark and the magnetic pole you can see that I actually live quite
close to it and the magnetic field of the Earth comes from the liquid outer
part of the core deep inside the Earth.
So I'm more or less living on top of a magnetic pole.
Here's a simplified illustration taken from Rick Hoadley's website.
His website is a treasure chest of information about magnetism.
The magnetic poles are constantly moving a little but geographic north pole is around here
and I live around here.
Notice that the magnetic field lines are going into Earth at a low angle and not just following
the Earth's surface. It is this angle into Earth that strong magnets tend to follow.
Where I live the north pole on a magnet prefers to point a little into the Earth.
That's why a neodymium magnet flips around when free-falling.
It also explains why I should put north pole against the copper. If I put north
outwards the magnet prefers to flip a little away from the copper
and then gravity takes over and pulls the magnet off the copper.
With north against the copper it's harder for the magnet to flip without
lifting itself so it's more stable against the copper letting the
eddy currents do their job.
Another tip is from Chris Andonoski: Increase the efficiency by cooling the copper.
I only tried cooling it to -18 degrees Celsius - because that was easy -
but it was enough to improve.
Search Youtube for eddy currents in copper cooled by liquid nitrogen.
It's awesome!