Kind: captions
Language: en
[Applause]
I have a pipe.
Yeah.
Do you want to hold it? Do you know what
it's made of?
Metal.
Is it brass?
Copper.
Is copper magnetic?
No.
Uh-oh.
I'm going to go no. I didn't think it
was. Go.
I'm going to go yes.
Well, why don't we check this is a
magnet.
And I'd like you to use it to test
whether the copper is is magnetic.
No.
I want you to be 100% sure here.
What do you think? No,
it's not magnetic.
I said so.
Okay.
Is there anything in there?
No.
What do you see in there?
That's nothing.
So, why don't we drop something through
it and just make sure it's empty, right?
Okay. This is not a magnet. So, this
isn't a magnet, but let's see what
happens when we drop it through.
That was a dull experiment, wasn't it?
Yeah.
Yes.
Okay. So, what's going to happen if we
drop this magnet down the pipe? Going to
pull first. Pull.
Let's do it. Three, two, one.
That was weird.
That's well cool.
Do it longer.
What's slowing the magnet down?
It's got to be magnetic poles or
something. I don't know. North, south.
Something to do with the polarity of the
north and the south poles.
But it doesn't stick. But then it's not
magnetic, so it shouldn't do anything,
right? You guys saw that.
That is slightly magnetic on the inside
somehow.
It's going to be magnetic inside, isn't
it? Or something.
[Laughter]
Does it like
kind of seals?
I think it's the powers of the universe.
I don't know. I don't know why it's
doing it.
Well, this is what's exciting is only a
few blocks from here was the lab of a
guy called Faraday. In October 1831, he
built the world's first electric
generator here. A magnet which you push
and pull in a coil to generate electric
current.
So that's the actual
Yeah. world's first electric generator.
And there's a permanent magnet in the
middle.
There's a permanent magnet. Yeah.
It was Faraday who realized that it's a
changing magnetic field that actually
can generate electric current. So, as
the magnet is falling through the pipe,
it's creating a changing magnetic field
that generates little electric currents,
so-called eddiurrens in the pipe, and
they create an opposing magnetic force
on the magnet, slowing it down.
So, it actually turns the pipe into a an
electromagnet.
I see.
Which pushes the magnet up. And this is
what's known as electromagnetic
induction.
So, it causes my LED to light up there.
But it's important that you move the
magnet quickly because if you move it
too slowly, the magnetic field is not
changing fast enough to generate enough
voltage to light this LED. This is
actually the way all electricity is
generated.
Is it?
Yeah. You move a magnet near a conductor
and it creates electric current. But
where is this electrical energy coming
from? You can't get energy for nothing.
Well, Faraday realized that there must
be a force pushing back on the magnet.
It's the same force that slows this
magnet down as it falls through the
pipe. So there's actually energy being
converted from gravitational potential
energy into electrical energy and
eventually to heat. So this pipe is
warming up by taking some of the energy
out of the falling magnet.
Is that any good or what?
Oh, it's very good.
This way. And these currents coming
around this way will induce a magnetic
field pushing in the opposite direction.
We took a grape and cut measure it out
length of 5.
You would find that it's about 12 lb
that
and then after that
find the best Nice.