All language subtitles for LS4U1B3

With that discussion in our head, let's
now write our simple definition

of the electric potential.

Electric potential.

So it is a scalar field.

Now let me stop there, and tell
you happy you should be

it's a scalar field.

OK?

So when we-- in this class, we've done
now three learning sequences.

We're in the fourth learning sequence.

So in the on-campus class, that's
basically a learning

sequence per week.

So I told the students in the first
three weeks, we're going to hit them

with a lot of math the
first three weeks.

The very first week is all vectors.

You've got to be really
good at vectors.

The second week we set up integrals.

You've got to be able to be
very good at setting up

integrals and solving them.

And the third week, we do
vector calculus already.

So sometimes by the end of the third
week, students that are really

struggling in math are very depressed.

And they don't think they're
going to make it.

So I'm going to tell you,
that's it for awhile.

OK?

We've done all the new math.

If you're kind of hanging in there with
all that stuff, now we get to

just use it.

We're not going to introduce a new math
concept every learning sequence,

every week.

We're kind of done.

For instance now, we're
taking a step back.

It's a scalar field.

It's not a vector field.

So it's actually a little bit easier
to use than the E field.

It's just-- it makes sense,
electrostatically,

to bring it in later.

But it's actually mathematically
simpler, because there's no direction

to worry about.

It is just a simple scalar field.

So if you're feeling lost in the math,
and you're thinking of giving up--

don't give up.

This is not the time.

Because the math is about
to calm down.

OK

So it is a scalar field that is equal to
the electrostatic potential energy.

Energy.

That's what we're talking about when we
thought about the test charge being

close to the big charge, or far from
the big charge-- the difference in

potential energy.

Not the same as the potential.

It's the potential energy.

And we'll be calculating it, and talking
about it in more detail.

Per unit charge.

This is what makes it special.

Per unit charge.

This is how it's analogous
to the electric field.

The electric field is the
force per unit charge.

This is the energy per unit charge.

Here's the confusing part.

Relative to some point where it
is defined to be zero, which

is usually far away.

This definition is getting a little
bit, not too technical.

Usually far, far away--

but in this galaxy.

That's about as simple as I can get
to bring all the points in.

Scalar field-- good news, it's
energy per unit charge.

You got that idea.

This relative part is tricky because a
lot of times when we talk about the

potential, we might call it delta-v.
We'll be calling it that soon.

Because that indicates it
really is a change.

But sometimes we get lazy and we just
call it v, which indicates maybe it's

not a change.

So you've got to keep up with--

is it an absolute number,
is it a change?

What's the deal?

So we'll be talking about
that quite a bit.