- [Diana] Thanks to Curiosity Stream
for supporting PBS Digital Studios.
Guess what kind of magnet this is?
- Wow, and why on Earth would a magnet look like that?
- I thought you'd never ask!
How do you do your intros?
What's up, MKBHD?
- What's up, guys? MKBHD here.
- You say what's up guys?
- Welcome to... - What about the girls?
- What's up, everybody? (Diana laughing)
- Hey everyone, I'm Diana.
You're watching Physics Girl
and I'm here in a very special place with MKBHD
in your studio, your office, your space?
- Thanks for coming through, yeah.
- Yeah thanks so much for having me here.
- You brought some magnet paper.
- I did. - Which is
my new favorite thing.
- And I know that you already made a little video
with magnet paper because I saw it
and I was like, "Oh, I really wanted to do that
with devices.".
Figured you have the biggest collection
of anybody I know.
- That's my secret, when I got it,
that was the first thing I wanted to try,
was just seeing what has magnets in it and what doesn't.
I'm excited to see what else we find.
So there's dozens,
I think hundreds of magnets in the iPad.
- Yeah.
- But if you look at the magnets here,
they line up with the same magnet array here.
And then they just snap right into place.
- Well I'm not using the fresh one yet.
- Okay. - I just wanna get a sense
for like where these are.
- All right. - But then I'm gonna let you
use the fresh magnet paper. - I'm excited.
- Yeah.
- Oh crazy, that's super cool.
This is the one that you already did.
- Yeah. - I remember seeing this array
of magnets.
Is it time to use the fresh magnet paper?
- I would love to.
(Diana laughing)
- Is this what you wanna use it on?
- Sure.
Wanna do the back?
- You only have two chances, choose wisely.
- Okay, I'm gonna pick up this fresh piece.
Let's try the back of the Galaxy S10.
This is like unwrapping a new phone.
- Never been used before.
Ooh, that is nice.
- Where did that...
That was not on the front, was it?
- That is nice.
Yeah, that was the one we saw on the front.
It was just a lot...
- Oh, it's just a lot more visible.
I know in the iPhone,
there's a much larger haptic engine, is what Apple calls it,
which is a vibration motor, than in many other phones.
- [Diana] Alright, so there's clearly
some magnets on the bottom there.
- [Marques] That looks very similar to the speakers
on the last phone.
Top of the magnet paper
to the top of the iPhone. - Is this auto-focus on?
- That's pretty good.
- (Diana laughing) - [Diana] It's awesome.
- [Marques] So there's your earpiece speaker.
I think if you ask most people
where they thought the speaker was,
they would just point to the grille.
When the grille is in one place,
the actual driver isn't exactly behind it
so it'll kind of just use this resonance chamber
and eventually make its way out the side
or front of the phone. - Oh, that's so cool.
- [Diana] Magnet paper, or magnet film,
shows you where magnetic fields are.
But how?
Yeah, so with one magnet,
you just get kind of a single pattern.
With a single simple magnet,
the North and South poles of the magnet show up dark
and the middle of the magnet is bright
because there's actually metal floating
in the middle of the paper.
The film is made of an oily substance
with a bunch of tiny pieces of nickel in it
sandwiched between two pieces of plastic.
So basically it's laminated sticky oil with metal flakes.
The oil holds the nickel flakes essentially in place
but they can still twist and turn which is they key.
You know how there's that demo
where you can take iron filings
and they line up with magnetic field lines around a magnet?
And also how fluids that have iron in them
will line up with the magnetic field lines?
Keep that in mind.
So I'm gonna suggest that you hold them
so that they don't fly away.
- Cool, they might fly away if I don't hold them.
- No they won't fly away.
- Don't fly away.
Whoa.
Fields.
(Diana laughing) Are you seeing that?
- [Diana] Oh yeah, I'm seeing that. Are you seeing that?
- [Marques] That's weird!
I don't know how to feel.
- You should feel excited and pumped because it's science.
- I'm learning. I'm definitely learning.
That is crazy though.
- [Diana] Isn't it cool? - [Marques] Wow.
- [Diana] Ferrofluid lines up with these
imaginary magnetic field lines
and in the same way, the nickel pieces in our magnet paper
will line themselves up with field lines.
On the sides, the nickel stands upright
and on the top it lies flat.
And where it lies flat, the nickel reflects light
like a mirror so it looks brighter.
On the sides, it'll look dark.
So both the dark and light parts
are part of the magnetic field.
They just show us where the magnetic field
is pointing perpendicular or parallel to the paper.
Which means, sadly, we can't tell North from South
but you can tell where the magnets are
even when you can't see them.
(Upbeat jazzy music)
So let me jump to this refrigerator magnet already.
- [Marques] Wow!
And why on Earth would a magnet look like that?
- I thought you'd never ask.
This is a plain old refrigerator magnet
and most of them look like this.
This is where magnets get weird.
That this is obviously one magnet.
I've got another one so I can show you it's not a trick.
- [Marques] What? - [Diana] Same thing.
- If you rotate it, do the lines rotate?
- Yeah, they sure do.
- [Marques] That's crazy.
- [Diana] Well I could also rotate the magnet, but yeah.
- [Diana] This is a special kind of magnet
called a halback array.
The magnetic field on these magnets is designed specially
so you can feel the magnet on one side but not on the other.
So you get really not much. - [Marques] Very faint.
- [Diana] Very faint, and then on this side,
the lines come through really clearly.
The way you get a magnetic field
on one side and not the other
is by making the magnetic field do something like this.
You get a North here, a South here, and back and forth,
and you make them by taking a mix of rubber
to make them flexy and iron to make them magnetizable.
You magnetize them by heating them,
applying a magnetic field to the material,
and cooling them down.
They usually only become demagnetized if you heat them up
except...
Put the magnet paper over this magnet.
- [Marques] What?
- [Diana] 'Cause I've been making you predict all along,
like a scientist, what do you think happened to that one?
- [Marques] That's so...
I don't know how it turns into this. I have no idea.
- I'll show you what happened.
- Oh. Wow.
- So now take that magnet off and look again.
- Okay.
(Diana laughing) - Put it very far away.
- [Marques] Wow, that's all it took.
- [Diana] Yep.
So either you need to heat up the magnet
to change the magnetic field,
or you need a magnet that's just way stronger.
I'm gonna bring this magnet closer.
Can you see those lines? - [Marques] Whoa, yeah.
- Yeah, so I'm actually affecting
the magnetic field of this magnet with this one
'cause it's so strong.
And if you get it close enough,
it'll affect it permanently.
It'll stay sort of warped.
- [Marques] Wow. - [Diana] Yeah, it's so cool.
- [Marques] It's like playing a guitar.
Like a magnet guitar.
- [Diana] Yeah, but then you get it too close
and then it'll permanently stay.
(Diana giggling) - That's crazy.
- Thanks!
- Thanks for teaching me.
- Thanks for getting excited about the science.
Oh! At the end of my videos,
I usually say happy physics-ing.
Like science-ing. I'm gonna science,
but instead, it's just physics.
Are you down to say that?
- I'm down.
- [Together] Happy physics-ing.
- Thanks to Curiosity Stream for supporting PBS.
Curiosity Stream is a subscription streaming service
that offers documentaries and nonfiction titles
from a variety of filmmakers
including Curiosity Stream originals.
For example, they have Exploring Quantum History
with Brian Greene.
A title that explores the origin
of one of the most unusual areas of physics.
You can learn more about Curiosity Stream at
curiositystream.com/physicsgirl
(Upbeat orchestral music)