Now we're going to change gears and talk about Inductors for a few moments.

Now, inductors are devices that store Magnetic Flux.

And the first thing we have to do is define what we mean by Magnetic Flux.

Now, let's assume that we have a coil of wire like this, and it has an area A,

we'll call A the variable for the area. And let's assume that we're running a

current through this coil of wire, that comes back out the other side.

Well, that current is going to give you a magnetic field.

That's going through the center of loop and it also goes around the outside and

back through, so it sort of loops around the wire.

But, there's a certain amount of magnetic field penetrating the area, the fields

cutting through the, the, the surface of the loop.

Now, the magnetic flux is defined to be the magnetic field strength times the

area. And so, that's the total magnetic field

multiplied by the area of the loop gives you the total magnetic flux linking that

loop. Now, the other thing that we need to

introduce here is Faraday's Law. So, this is kind of a crash course of

half a semester of electricity magnetism. But, we're going to just hit the high

points here that we need for this course. Now, Faraday's Law says that for this

configuration, this loop over here. If the magnetic flux changes over time,

then a voltage is going to appear across these terminals.

And so, you only get a voltage here if the magnetic flux is changing over time.

If you just, if there's a steady current and an unchanging magnetic flux, then

there will be no voltage appearing here. Now, the the other thing that note here

is that the, the voltage is increased if I add more turns.

So, imagine I made a coil that had ten turns of wire.

And I had a certain magnetic flux linking all ten turns than the, if phi is the

flux through one turn, then if I have n turns or say, n equals 10.

Then, I'll have ten times the voltage. And so, I have to multiply this by the

number of terms. Now, the other thing to notice is that

minus sign. And that minus sign comes about, from

something called Lenz's law. And Lenz's law just says that a change in

magnetic flux generates a voltage that tries to drive a current that's going to

produce a magnetic field that opposes the change.

So, in other words, the, this coil doesn't want to change the magnetic flux

inside. And if I try to change the magnetic flux,

then there's going to be a voltage induced by that change.

Such that its going to try to drive a current that's going to oppose the

change. And so in a sense, coil kind of light the

way it is, it doesn't want to make magnetic flux to change.

That's where the minus sign comes from. So these, this is I realize I'm just kind

of pulling this out of a hat but this is the some of the essential pieces from a,

an electricity and magnetism course. That we need to really intelligently

discuss inductors. And I just have to ask you to take my

word for this, or go look it up on pick up a book on electricity and magnetism.