This episode was made possible by generous
supporters on Patreon. Hey Crazies. There’s a question I get every once in a
while that I think we’re ready to answer: What the heck is electric charge? Let’s just jump into it. I don’t even think we’ll need quantum
mechanics for this. Just like objects can have mass or temperature or speed, objects can also have charge. It’s just a property. Things like balloons, hair, or pieces of plastic
become charged by transferring electrons. Super zoom! Inside atoms, protons and neutrons are the
heavier particles in the center. Electrons are the lighter looser particles
on the outside. So they’re what can be gained or lost when
things rub against each other. If we rub a balloon against someone’s hair, the balloon and the hair become attracted to each other. Now that they’re charged, they don’t even
need to touch to affect each other. This is just like how masses attract in Newtonian gravity. We even said in the previous video there were
a lot of similarities, so this shouldn’t be a surprise if you’re already subscribed. Subscribe. Unlike mass though, charge has two different types or flavors. We call these two types: positive and negative, but only for mathematical convenience. They’re just labels. We could have just as easily called them:
Up and Down or Good and Evil, or Dingleberry and Snozberry. The snozberries taste like snozberries. The two types show opposite behaviors,
so as long as the labels are opposites, we’re fine. It doesn’t even matter which one we label
which. The labels we use today were decided 270 years ago in 1748 by Ben Franklin. It might have been better to label them the
other way, but now we’re stuck with it. Thanks Ben Franklin. Hop on my filthy back! Anyway, where was I? Oh, oh right! Opposite behaviors! Opposite charges attract and like charges repel, which I think is pretty common knowledge at this point. That’s what makes atoms the way they are. The protons are positive and the electrons are negative, so they’re attracted to each other. Unfortunately, since the electrons are the things that move around and electrons are negative, we kind of have to think backwards. An electron gain makes an object negative
and an electron loss makes an object positive. The balloon from earlier gained electrons
from the hair, so it became negative and the hair became positive. But that doesn’t really explain what charge is. As Cameron McHenry pointed out, sure objects become charged because their parts are charged. But electrons are elementary particles. They don’t have parts and neither do any
of these other charged particles. So what the heck is charge?! To answer that, we need to talk about the EM field. Charge and the electromagnetic field are inextricably connected. You can’t really understand one without
understanding the other. What’s a field again? Yeah, OK, that’s a fair question. A field is a value or set of values assigned
to every point in space. But jumping right into the EM field can be
a bit overwhelming. Let’s start with gravity. It’s a little easier to imagine and a lot
easier to work with. So, here’s the Earth. Just chilling. Around the Earth is a bunch of points in space and every single one of those points has a vector arrow attached to it. Since the Earth is pretty massive, it has
a lot of control over those arrows. The whole collection of arrows is called a
gravitational field and it’s always there. Even if there isn’t any mass around, the
field is still there. It’s just zero. It helps to think of mass as a property of
objects and fields as a property of space. The Earth and the space it occupies are real tangible things. The mass and the field are just properties we measure to help us explain what the tangible things are doing. And a really convenient way to understand
that connection is with Gauss’s law. In general, it’s written like this. Here’s the field, a property of space, and here’s whatever property is affecting that field. For gravity, it relates the gravitational field to mass. It says the gravitation field across some
closed area, also known as flux, is proportional to the mass inside that closed area. Ugh, can you do that with a picture please? Oh yeah, yeah, yeah, sure thing. Let’s imagine that closed area is the surface of a sphere. If that sphere doesn’t enclose any mass,
then there’s no flux across its surface. There is just as much field pointed in
as there is pointed out. If that sphere does enclose mass,
then there’s an overall inward flux. There’s more field pointed inward than outward,
which is true no matter how big the sphere is Even if you don’t know where the mass is,
the field’s behavior tells you where the mass is and how much there is. It’s actually a really useful connection. Because electricity is so similar, we can
do the same thing with the EM field and charge, but the EM field is just a smidge more complicated. We could look at it all together as an electromagnetic tensor, one big set of numbers attached to each point in space. But it’s easier to think about it as
two separate vectors instead, one for the electric part and one for the magnetic part. Vector fields are so much easier than tensor fields. Trust me. You don’t want to use the tensors unless you have to. So we’ll imagine each point in space has
two vector arrows attached. As a charge moves around inside the space,
you can see how each of those vectors changes. If the charge isn’t moving, then all the
magnetic arrows drop to zero, leaving only the electric arrows. We’ll focus on that electric part now
and save that magnetic part for a later video. Back to Gauss’s law! For electric fields, it looks like this. It relates the electric field to charge. And just like with gravity, you can use a
carefully chosen closed area to figure out where the charge is and how
much of it there is. Just like mass tell us how much an object
or particle will affect the gravitational field, charge tells us how much an object or particle will affect the electromagnetic field. It’s coupling property. It couples objects and particles to space. So what’s electric charge? Electric charge is just a property of objects or particles that inextricably connects them to the EM field and, therefore, to space. There are two opposite types that display opposite behaviors. It’s conserved across time and everyone agrees on how much there is. It’s a really big deal! So, was this deep enough for you or are you still craving the quantum mechanics? Let us know in the comments. Thanks for liking and sharing this video. Don’t forget to subscribe if you’d like to keep up with us. And until next time, remember, it’s OK to be a little crazy. The featured comment comes from Zoltán Kürti who mentioned: Gauss didn't use vector fields. He used quaternions. Yes, I know, vectors weren’t all that universal
until Oliver Heaviside came along, but quaternions are really confusing. If you’re interested though, 3blue1brown
did a good video on them recently. Link in the doobly-doo. Anyway, thanks for watching!
