Name: レンツの法則 (Lenz's Law)
Uploaded: 2021-01-14T10:29:00.000Z
Duration: 15 min 54 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

様態の副詞

Welcome to Michael's Toys the first and only show on YouTube made by, of, and for teenagers who like to cook

We are going to be talking about magnets, specifically the strongest magnetic field my body has ever been inside

Which I guess kind of makes this an episode of UC Irvine's toys because they own the MRI, I don't.

My brain for MindField season two and I learned a lot about them, and they are... just beautiful and wonderful.

Here's a question how strong are different magnets?

Well, one way of measuring a magnet's magnetic field strength, really its magnetic flux density, is the tesla.

Alright now to put a tesla into perspective, our planet is a big magnet, really.

It's not a really strong magnet though– its magnetic field strength is just about maybe 31 microteslas.

In comparison and everyday ordinary refrigerator magnet has a magnetic flux density of about maybe like five milliteslas.

A typical sunspot can have a magnetic flux density of around a third of a tesla, but the surface of a neodymium

rare-earth magnet can have a magnetic flux density around 1.25 tesla.

The MRI machine I got in many many times for MindField season 2 was a 3 tesla machine

Which means you can do some pretty weird things with it. You have to be very very careful:

No ferromagnetic metals are allowed into the room it is in, or even near it in the room outside because it attracts

ferromagnetic materials so quickly that they could be pulled from your hand race through the air at an ever-accelerating rate

until they strike the machine at, like, super-lethal and at least very dangerous speeds.

There are videos on YouTube where people show off just how dangerous the

magnetic power of an MRI can be: it can lift chairs off the ground, but what about metals that aren't attracted to magnets?

Well, they exhibit some v ery strange behaviors and Craig Stark at UC Irvine

was kind enough to allow me to bring in a giant block of aluminum

Now I'm gonna have to just talk over this clip because we obviously couldn't bring cameras or microphones

into the room to pick up our voices we had to set the camera far away and then zoom into myself pause

Let's just take a brief moment to appreciate the tan line on my face caused by my glasses

But here's an aluminum block and I'm gonna set it up on its side, and then let it fall okay, pretty easy

But watch what happens when I set the aluminum block near the inside of the MRI and let it go

But not really. It's actually a demonstration of Lenz's law

Veritasium has a fantastic video on the topic and I see it coming up on Reddit

Quite frequently so I had to do it myself, it's really fun these are very powerful magnets

And I'm gonna drop them so that they fall

Only due to gravity. Here we go: three, two, one

there it is 9.8 m/s^2, for those of you counting at home, but now I'm gonna drop them through a copper pipe.

Copper has no interest in magnets, or maybe magnets don't care about them

Or do they? Well we're gonna find out. Notice that if I try to stick the magnets magnets to the copper, it not

They fall really slowly. Here we go one more time three two one

Something's slowing them down. You can hear that they are hitting the sides of the copper

But they don't have to do that if my magnet was a better shape it wouldn't happen, and they would just glide right on down

They really are more slowly. Let's look at it from above.

Here are the magnets being dropped by themselves.

That's how long it takes for them to fall to the table

But now let's drop them through this copper pipe. Okay ready three two one

Look at that! Let's try it one more time.

Three, two one, and they hit. Much much slower.

To see what's going on, let's play around with magnets. One of my favorite magnetic fun recipes is a one that I learned from Science Bob

It involves breakfast cereals and a bowl of water.

So here's my bowl of water now what I need to do is grab myself one little flake of this corn flake-like cereal

Now many breakfast cereals are fortified with iron

And it's not iron in any kind of compound. It's literally just elemental iron.

If I float a little piece of cereal there in the water looks pretty boring

Ohhhh! Look at that! It follows the magnet! I'll come in from the other side so you can see that

it wasn't just some sort of property of the water

Look at that! I'm able to move the cereal across the water by attracting the iron inside it with a magnet.

When you eat many foods you're eating just straight-up elemental iron like the kind

We make nails out of just like a lot less than would be in a nail. Oh I love that

I hope it's clear for you guys to see this demo wasn't really related to MRIs

I just thought it would be really fun to do to really start talking about why that block of aluminium fell

So slowly around that strong magnetic field we need a more advanced recipe

but I think you guys are ready for it what we're gonna need for this recipe is a

You're also going to need... let's see this one looks good

You're gonna need some copper wire that's thinly insulated.

You might need more than this, but what you're gonna want to do is take your wire and coil it around your nail.

Keep them all bunched together, so you get as many wrap arounds of the wire around the nail as you can get and then

You'll want to connect the two ends of the wire to a battery now

That might take a while so because of the magic of a TV cooking show I prepared an electromagnet earlier

Oh yeah it's ready, this is good this is really good.

Just like mom used to make. Um, we've got here a big battery,

and we've got a nail that is just coiled with lots and lots of wire. I think that

We let the paperclip simmer long enough. I'm gonna go ahead and put them

There on our aluminum foil and I'll demonstrate that at this moment

Because the wires are not completing a circuit the nail

Is not magnetic, has no effect on the paper clips

But now let's connect this wire to the negative terminal and see what happens

All right, so what we've learned is that current flowing creates a magnetic field.

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レンツの法則 (Lenz's Law)

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strength

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