Kind: captions
Language: en
How much does this thing weigh? Well,
try and pick it up. Okay.
Which is which is Okay. All right. Yeah.
Yeah. Be nice to 105 lbs. 105 lbs. It
consists of four motors connected up to
these spinning magnet arrays. And if you
spin these fast enough, it will actually
levitate. That's correct. Let's see if
it can do it. You ready? Let's fire it
up.
It's
lifting. Okay, it's flying now. Is it?
Yeah.
Now it is so easy to just move around.
That's amazing. Give it a push. Like
it's got some real
Wow. It can carry some weight. Hey.
Yeah, that is
amazing. So, how does it work? Well,
it's similar to how a magnet falling
through a pipe is slowed down. Anytime a
conductor experiences a changing
magnetic field, electric currents are
induced in it, which create a magnetic
field to oppose that change. And in this
case, the spinning magnets induce
currents in the copper sheet. They
create a magnetic field which is nearly
a mirror image of the spinning magnets.
And so they're repelled. If the rotors
spin fast enough, this repulsion leads
to levitation. That is awesome. All
right, let's set it down. Yep.
So, it's just going to come gently land.
The induced currents then encounter
resistance in the copper, so they
dissipate their energy as heat.
Wa. And this copper is pretty hot. It's
gotten warmer. Yeah, I can still keep my
hand on it at least for a second or two,
but it is like like a hot mug of coffee
or something. Yeah, I experienced this
before with another electromagnetic
levitation device, except with this one,
the changing magnetic field was created
by an electromagnet in the base,
inducing currents in a light aluminum
plate which levitated. Wo! The plate got
so hot you could boil water on it. Check
out how hot this plate is. If you have
two north magnets facing each other,
they normally just kind of like fall
off. Yeah. Is there a similar problem
here or no? Uh, not really. No. And the
reason is the magnetic fields that are
induced by currents in the copper sheet,
uh, a mirror image of the applied
magnetic field. Um, and the effect is so
quick that that as it as it moves, it it
just kind of follows it around. Making
this device work in practice is harder
than it looks. For one thing, the
magnetic field of the permanent magnets
has to be very strong. Neodymium magnets
are strong, but there's a special
configuration you can use to make them
even stronger. It's called a halbach
array. They're used in particle
accelerators. They're used in um fridge
magnets actually arrays. So, they're
stronger on the side that sticks to the
fridge, so use less material overall.
Magnetic field lines run from north to
south, and they're normally symmetric on
both sides of a magnet. But if you
rearrange them like this, the magnetic
field lines are channeled almost
entirely into one side of the magnetic
array and they cancel out on the other
side. This configuration produces a much
stronger magnetic field without changing
the properties of the magnets. In these
rotors, there are 12 wedge-shaped
magnets. Their magnetic poles are fixed
in this particular arrangement. This
increases the magnetic field on the
bottom side and almost eliminates it on
the top. As the magnets spin, they
create a rotating magnetic field in the
copper beneath them. This induces
currents that create magnetic fields
which oppose the magnetic field of the
spinning magnets above. The result is a
repulsive force that is effectively lift
for this quadcopter. But in addition to
lift, there is also drag. Energy is
clearly being dissipated in the system
as the heat produced by the induced
currents in the copper. And that energy
comes from the fact the magnetic field
of the induced current is not a perfect
mirror of the spinning magnets above.
Instead, the induced magnetic poles are
slightly ahead. So they produce a
backward force on the rotors, which is
really a backwards torque. And that's
why the rotors on alternate corners have
to spin in opposite directions because
otherwise they would produce a net spin
and turn the whole machine in one
direction. This way they cancel out.
This principle has been used to achieve
levitation in everything from mag lev
trains to hoverboards. And it's being
considered as a means to make the
hyperloop, a superfast system for
transporting people and goods through
tubes at very low pressure. But instead
of spinning the magnets, the vehicle's
motion itself would cause the magnetic
field to change in the conductive track
below. So in the future, do you think
this is going to be how we travel? I
think like ongoing developments in
digital motor controllers and uh very
powerful magnets will mean that uh
talking about moving humans and cargo at
extremely high speeds uh is actually
something that we can as a species kind
of look at and be like wow it turns out
that getting from one city to another
city in the same day is something that
the next billion or two billion people
might have the opportunity to do in one
lifetime.
Hey, Veritasium is supported by viewers
like you on Patreon and by Audible.
Audible has an unmatched selection of
audio books, plus original shows, news,
comedy, and more. And for viewers of
this channel, they offer a free 30-day
trial of their service. Just go to
audible.com/veritassium. Now, if you're
looking for a good book recommendation,
uh maybe you can try out the one I'm
listening to right now, which is Elon
Musk, Tesla, SpaceX, and the Quest for a
Fantastic Future by Ashley Vance. This
is a biography about one of the, in my
view, most impressive entrepreneurs
alive today. And uh this book was
written by interviewing hundreds of his
employees, his acquaintances, and Elon
Musk himself. And so it provides a
really in-depth and thorough look at
that incredible determination that's
made possible all of Elon Musk's
ventures. So if you're intrigued by him
and his work, then you should check out
this book. And you can download it for
free by going to
audible.com/veritassium or you can pick
any other book of your choosing for a
one month free trial. So I want to thank
Audible for supporting me and I want to
thank you for watching.