Okay, what we're going to look at that is how we generate electricity.
Okay, so what we want to do--this is called Lenz's Law--is figure out, when a magnet is moving near coil, which way will
electricity flow? First thing you got to remember is:
moving a wire near a magnet will cause the current to flow or moving the, the magnet near
the wire. Either way, if the two are moving near each other, you're going to get electricity to flow.
The question is which way is that electricity flowing? And, as I said before, in other videos, if you're told to use the right-hand rule,
use the right-hand rule. You'll get the appropriate answer for the right-hand rule.
If you're supposed to use the left-hand rule, use the left hand rule and you'll get the appropriate answer.
So, let's take a look at this.
I've got a magnet moving near a coil. When electricity--
when, when a magnet is moving near a coil, in or out of a coil,
it will cause electricity to flow in that coil.
We want to know which direction it's flowing.
So, I've got a coil here,
I've got a magnet. And, the north is going into the coil.
And, I'm not going to get into a big explanation about why,
we'll just accept it at this point because we want to know how to get the direction of electricity flow.
What you got to know is: whatever this magnet is doing, it's going to make electricity flow in this coil.
That means when electricity flows in this coil, it is acting like an electromagnet.
And, this electromagnet is going to be in such a way--the north and the south--to make this difficult.
So, whatever the magnet is doing,
the coil must do something to make it difficult for the magnet to do what it's doing. That way,
conservation of energy works and we get electricity to flow.
So, if I'm pushing in north, into this coil,
how could I make that difficult?
Well, if this was a cell,
then that north would be attracted to that cell. So, as I'm pushing the magnet into the coil,
It would actually be helping me, pulling that magnet into the coil.
So, that's not right.
If this end of this coil becomes or acts like a north, then as I'm pushing this north in, this north is trying to stop
it. It's making it difficult for me to push that back in it and that's the way it works. So,
If this north is going in, then this must be in a pole that makes that difficult. So, what that means is
this must be a north and this must be a south. This north makes it difficult to push that north in.
So, now I use my right hand or left hand rule, depending on what you're using in your class.
I'm using the left hand rule.
With the left hand rule, I treat this now like an electromagnet.
Electricity is flowing through this.
I've generated electricity in
such a way that my thumb points to the right
and my fingers point in the direction of the
electricity flow. I put my thumb like that.
The electricity is flowing up, on the top of this coil,
if I use the left hand rule. So it's going this way:
up here and down there.
Let's try another one.
Here's another coil.
I'm taking my magnet and this time, I'm pulling the magnet out.
How can I make that difficult?
Electricity is going to flow in here in order to make the poles of this make this difficult. Well,
if I'm pulling the north out--if this is south,
then that south is trying to pull the magnet back in and I'm pulling the magnet out. It's making it difficult.
That's the way the rule works.
So, this is south, this is north. I treat it like an electromagnet.
If this is north and this is south in a coil, which way is electricity flowing?
If I'm using the left hand rule: put my thumb
this way, grab it. My fingers are down in the front,
so they must be, the electricity must be flowing that way.
If I'm using the right hand rule, it's a different answer, but it's appropriate for the book I'm using. Okay?
Let's look at a third one.
This is the south being pulled out of a coil.
If a south is being pulled out, I need to make this a north.
The reason is
this north is trying to pull this south back in
and I'm trying to pull this south out. That's making it difficult.
So, if this is a north and this is a south, I got my coil.
My thumb's got to point to the right.
The fingers, therefore, are going up.
And, since my fingers are going up,
the current flow is that way.
So, when I do this,
this is the way the current's going to flow.
Let's look at this one here.
I know the direction the current is flowing.
I got my magnet
and I want to know is this magnet is being pulled out or pulled in--or pushed in?
So, I go here.
I, I know the direction of the current.
My fingers go down and out front.
My thumb is, therefore, to the left.
So, this must be a north and this is a south.
This electromagnet: this is north,
this is south.
I'm generating that current by moving this magnet.
Which way am I moving it?
If this is the south and this is a south, they're repelling.
This south is trying to push the magnet out.
I've got to do the opposite.
That's making it difficult.
If this south is going in and this is south, that's making it difficult for me to push this in 'cause it's repelling.
And, as a result, electricity will flow that way.
So you can do it either way. I hope that helps.