Okay.  Before you watch the video on the coils and
electromagnets, I want to clear up something to make sure there's no problems.
I'm going to be teaching a video on the left hand rule.
And, I'm going to mention the right hand rule is very much the same:  you apply it by using your right hand.
And, it's really very simple. Don't let it confuse you.
If you're supposed to use the left hand,
check with your teacher, your textbook, it'll say left hand rules, use your left hand.
If your textbook says or your teacher says, "No,
we're using right hand rules, then use your right hand.
The problem
I'm anticipating is that I'm going to explain the left hand rule and you're going to say, "Well,
I'm supposed to use the right hand rule. Let me try it," and you apply it and you get a different answer.  And,
you're like, "Hey, what's going on here?  It doesn't make sense."
Keep in mind:  the question in the example was based on the left hand rule, what we call electron flow.
If you're using this method, the conventional current and the right hand rule,
the question would have been different, the arrows for the
current would have been going the other way because of the different theory.  So,
follow--look at my example
If you're using the right hand rule, don't apply it to the example in the
video I'm making because it won't work properly.
But, trust me:
if you're supposed to use the right hand rule, the question was made by your teacher for the right hand rule, use
your right hand rule.
Just as I described the left hand rule, same usage you will get the right answer.  Okay, so let's watch the video.
Yeah, and it was made before I got by a haircut and I like this better, huh.
So, what we talked about was when electricity flows in a wire,
it creates a magnetic field, a dull magnetic field around
the wire.  And, we can figure out that direction (that was the previous video).
What we're doing now is we loop that wire
into a coil
and we create an electromagnet.  And, what we want to know is which side of the electromagnet is north?
So, here's a coil of wire.
I'm going to put electricity in it
and the electricity is going to go around the coil.  And,
depending on which way the electricity is going around,
this might end up north or this might end up south
and we have a very simple rule for them.
If you're using the left-hand rule,
the rule is your thumb points in the direction of north and your fingers are
In the direction of the flow of the current.  So, here's an example:
the electricity is flowing around something. This is not a magnet. It's not a piece of wire,
It's just a core of some kind, maybe it's an iron core, maybe it's a piece of plastic that you've wrapped this wire around.
So, the wire's wrapped around this way.
And, if I look at the way the current is flowing, it's flowing this way.  My fingers are going to flow--go,
point in the direction of the flow of current,
So, my fingers on my left hand
are going to wrap
this way, my fingers on the front are going to be going down.  As a result, my thumb is pointing to the left.
That tells me that the left side must be north.  Then, the right side must be south.
It's really, really quite simple.  Let's look at some examples.
Here's electricity flowing in a wire around something,
so there's a coil there.
If there's a coil there, then one side must be north and one must be south.
If I use my left hand rule,
that's okay
if electricity is flowing in such a way.  I take my coil--
in this coil, the electricity is flowing down on the front.
So, I grab the coil this way, with my fingers pointing down, just like that.
Now, my thumb ends up being on this side. This is north, this is south.
If you're using the right hand rule, it's very simple.
Which way is the electricity flowing?
Well, electricity's flowing this way
or the current's flowing this way,
then this must be north.
You just use the other hand, so it's no big deal.
The electricity is flowing this way in this coil,
so I'm using the left hand rule.
My fingers have to be in such a way that
I grab it so my fingers are pointing that way, across the front.
So, the bottom must be north.
This is north, this is south.
This coil here:
my fingers are grabbing it so that my fingers are pointing that way.
So, this ends up being my thumb down that way.
This is north, this is south.
Now, we might go backwards.
I might tell you which way is north and south
and you've got to tell me which way the electricity's flowing.  Very simple. Here's my coil.
The electricity is flowing in such a way that makes this north, so my thumb must be up.
How do I grab the coil so my thumb is up?
I grab it this way.  My fingers are going to the left on the front.
The electricity's flowing that way, which means it's coming in there and
Out there.  I just follow right behind the coil.
This one here:
the flow of current creates north at the bottom, so I've got to put my thumb down.
My thumb is down, my fingers are to the right on the front.
So, the current must be flowing that way, out here
and in there.
If you need to use the right hand rule, it's the same sort of idea.
You're not going to get the same answer.  Don't worry about that.  Use the right hand rule, too.
If this is north, then I point my thumb that way.
The electricity must be going this way on this coil.
And, that's basically the right hand rules for an electromagnet or the left hand rule for an electromagnet.
