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 that noise. What’s that noise? It’s the vibration of the plate, because it’s
vibrating at two times the frequency of this one. Woah! Woooaaaahhhhhhh!! hahaha, how does it do that? It’s magical 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 the lock still works. From the 1870’s on this became a store room,
which is why it survived and it survived intact, all the joinery giant electromagnet are exactly
the same as Faraday left it. So this is exactly as Faraday would have had
it. That’s right, yup. 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 x hundred meters of insulated wire, you had
to insulate the wire as you went. So as you pushed and pulled the wire in and out of the
ring you had to insulate it. It takes 10 working days, which was 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: 800A 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 lightbulbs glow. A gift.
Uh, thank you. Oh. That is cool.
Not too close because it will burn the lamps. Can I put it there?
Yeah. And just as current in a toaster element heats
it up, the induced current in the plate dissipates its energy as heat. And some water too
Thank you. Yeah to see the temperature.
Check out how hot this plate is. Oh, that is nuts! Is this your favorite demo?
It’s a flying BBQ or something Tell me this is not the best dinner table
centerpiece. It levitates, gives you light, and you can cook on it. and all the while
you’re demonstrating Faraday’s Law of electromagnetic induction.
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