Kind: captions
Language: en
Let's switch it on. Let's see what it
does. Through this coil of thick wire,
we're about to pass a huge alternating
electric current. On top is a 1 kg
aluminium plate.
So, we hear this noise. What's that
noise?
It's the vibration of the plate because
it's vibrating at two times the
frequency of this of the this one.
WA.
[screaming]
[groaning]
How does it do that?
To find out, I've come to the place
where it all started. The Royal
Institution in London.
This is the key to Faraday's magnetic
lab.
It's amazing that lock still works.
From the 1870s on became a store room,
which is why it survived. And it
survived intact. All the joinery, dry
electro magnet, uh exactly the same as
Faraday. Uh
so this is exactly as Faraday would have
had.
That's right. Y
in Faraday's time it was known that
electric current creates a magnetic
field. But it remained an open question
whether the reverse is possible if a
magnetic field could generate electric
current. Faraday answered this question
with his most famous apparatus.
Faraday's electromagnetic
induction ring
which is this.
In August 1831, Faraday wrapped two
coils of insulated wire around this iron
ring. But in 1831, you could not go down
to your local electrical hardware shop
and ask for 600 L of insulated wire. You
had to insulate the wire as you went.
And so as you pushed and pulled the wire
out of the ring, you had to insulate it.
It takes 10 working days, which is a
huge investment of time.
But the investment paid off. When
Faraday connected a battery to one of
the coils, he saw a brief pulse of
current in the other coil. And when he
disconnected the battery, he saw a pulse
of current in the other direction. He
realized that current was induced in the
second coil only when the magnetic field
through it was changing. And if they
hadn't been wrapped on the same ring,
Faraday may have noticed that the two
coils repel each other when the current
is induced. And that's due to the
interaction of their magnetic fields.
Which brings us back to this. Through
the bottom coil, we are passing a huge
electric current 800 amps, which
alternates in direction 900 times per
second. This ensures there will always
be a changing magnetic field above the
coil. Instead of a second coil, we're
using the aluminium plate, but the
principle is the same. The changing
magnetic field induces currents in the
plate that create an opposing magnetic
field so it levitates.
How awesome is that?
This current is not only good for
levitating the plate, it can also make
light bulbs glow. A gift. Oh, thank you.
Oh,
that is cool.
Not too close because it will burn the
the the arms.
Can I put it there?
Yep.
And just as current in a toaster element
heats it up, the induced current in the
plate dissipates its energy as heat.
Some water.
Thank you.
Yeah. To see the top.
Check out how hot this plate is. [bell]
Oh, that is nuts.
Is this your favorite demo? It's like a
flying barbecue or something.
Tell me this is not the best dinner
table centerpiece. It levitates, it
gives you light, and you can cook on it.
And all the while, you're demonstrating
Faraday's law of electromagnetic
induction.
But where do they get that matter to
grow?
There nutrients out the ground. Is that
all really? Yeah. Goodness.
Because the flame has those ions in it,
it means that we can break down a
greater distance of air with the
Why isn't there a big hole around the
tree where it's taken out all the soil?
Does it say so gradually that the soil
has time to recover? [laughter]