Name: 懸浮式燒烤!電磁感應 (Levitating Barbecue! Electromagnetic Induction)
Uploaded: 2021-01-14T04:39:34.000Z
Duration: 3 min 46 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

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.

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

To find out, I've come to the place where it all started - The Royal Institution in

This is the key to Faraday's magnetic lab.

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.

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

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

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

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

This current is not only good for levitating the plate. It can also make lightbulbs glow.

That is cool. Not too close because it will burn the lamps.

And just as current in a toaster element heats it up, the induced current in the plate dissipates

Yeah to see the temperature. Check out how hot this plate is. Oh, that

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

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懸浮式燒烤!電磁感應 (Levitating Barbecue! Electromagnetic Induction)

plate

change

noise

question