World's First Electric Generator

[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? Coer? Is copper magnetic? No? Uh-oh. I'm going to go. No, I didn't think it was. Go, yes! 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 magnetic. No, I want you to be 100% sure. 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? 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. [Music] That was a dull experiment, wasn't it? Yeah. Yeah. Okay, so what's going to happen if we drop this magnet down the pipe?

Going to pull free? Pull? Let's do it. 3, 2, 1! 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? TR 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 are there. That is slightly magnetic on the inside somehow. It's going to be magnetic inside, isn't it? Or [Laughter]? Something. Does it like—it kind of tilts? 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: 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 and out of a coil generates electric current. So that's the actual… yeah, world's first electric generator.

And there's a permanent magnet in the middle. That'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 Eddy currents—in the pipe, and they create an opposing magnetic force on the magnet, slowing it down.

So it actually turns the pipe into 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 gra—and me out, you would find that it's about 12 and then…