byRichard J. Terwilliger

Created byRichard J. TerwilligerJuly 2001

The magnetic field in front of the wire points towards the top of the page.

The magnetic field behind the wire points towards the bottom of the page.

The magnetic field above the wire points into the page.

The magnetic field below the wire points out of the page.

Again, The thumb of the left hand points in the direction of electron flowThe fingers curl around the wire in the direction of the magnetic field

The magnetic field in front of the wire is to the left

The magnetic field on the left side of the wire is back into the page

The magnetic field behind the wire is to the right

The magnetic field on the right side of the wire is pointed out of the page

Into the page is shown by an XOut of the page is shown by a dot

Into the page is shown by an XOut of the page is shown by a dot

Into the page is shown by an XOut of the page is shown by a dot

The current flow is now to the left

The current flow is now to the leftThe thumb points in the direction of electron flow,the fingers curl around the wire in the direction of the magnetic field.

The current flow is now to the leftThe thumb points in the direction of electron flow,the fingers curl around the wire in the direction of the magnetic field.

The current flow is now to the leftThe thumb points in the direction of electron flow,the fingers curl around the wire in the direction of the magnetic field.

Each of the following diagrams shows a section of wire that has been enlarged.Associated with each wire is the direction of current flow and the magnetic field around the wire.Determine which of the following diagrams are correct.

Arrows show the direction of negative current flow.Using your left hand, grab the wire with your thumb pointed in the direction of electron flow.Your fingers curl around the wire in the direction of the magnetic field.

Is the diagram at the left correct?The diagram is

Is the diagram at the left correct?The diagram is

Through the circuit and back to the positive side of the potential source.

Therefore the current flow in the green section of wire is down as shown.

Lets go back and try the problem again.

The compass needle points into the page

What is the direction of the current flow in the wire?Click on your choice above.

The magnetic field above the wire goes into the page as shown by the compass.

Your thumb points in the direction of negative current flow.

Your thumb points in the direction of negative current flow.

Negative current flow is to the right.

Lets review why.

As shown by the compass, the magnetic field above the wire goes into the page.

Your thumb shows the current is flowing to the right.

Your thumb shows the current is flowing to the right.

Shown here is a loop of wire connected to a potential source.

The electrons flow from the negative terminal of the battery

through the wire and back to the positive terminal.

through the wire and back to the positive terminal.

We know that when current flows through a wire a magnetic field is formed.

Fingers curl in the direction of the magnetic fieldThe arrows show the direction of electron flow.

Curl your fingers around the loop in the same direction as the electron flow.

Your thumb now points

The magnetic field on the outside of the loop is from the north pole to the south pole

The magnetic field inside the loop travels from the south back to the north

If we place a compass inside the loop it points in the direction of the flux lines

Outside the loop a compass still points in the direction of the magnetic flux lines

We could use one of the cardboard rolls found at the center of toilet paper rolls

The front side of the coil is called the face of the coil.

We will start creating an electrical solenoid by wrapping wire around the core.

Each wrap is a loop of wire.

and all the loops form a coil

The current will flow from the negative terminal

through the wire and back to the positive terminal.

and down the front side or face of the coil.

Current flowing through the coil creates a magnetic field.

Grasp the coil with your left hand curling your fingers around the coil in the direction of electron flow.

The magnetic flux lines come out of the NORTH, go around and into the SOUTH.

In what direction would a compass point if placed above the coil?

A compass will point in the same direction as the magnetic flux lines at that point.

Now we are going to replace this coil with another coil that has the wire wrapped around in the opposite direction.

The battery will still be connected with the negative terminal on the left.

Watch closely so you can see the difference.

Watch closely so you can see the difference.

The current still travels from the negative terminal through the coil and back to to positive terminal.

Notice that the electrons travel up the face of the coil, over the top and down the back

Notice that the electrons travel up the face of the coil, over the top and down the back

Your fingers will follow the electron flow.

Curl your fingers over the top and down the back.

Lets try another example.

Well start with another coil.

The coil is attached to a potential source but the polarity is unknown.

AB

AB

Now the

Remember that the magnetic field goes from

Or current flow through a conductor that is in the magnetic field.

I will now show you how to apply the

Point your fingers

Your thumb points in the direction of negative

And theacting on the current bearing wire or moving negative charge is out of the palm.

First point your fingers of your left hand

Notice that your fingers point in the same direction as the magnetic field shown by the symbol

And the force acting on the moving charge or current bearing wire is out of the palm.

So the force acting on the wire is

Lets try another example

Shown here is a current bearing wire placed between the north and south poles of a horseshoe magnet.

The electron flow in the enlarged section of wire is back into the page as shown by the arrows.

We can find the direction of the force on the wire using the

Using your left hand point your fingers

Now, keeping your fingers pointed south, rotate your hand so you thumb points in the same direction as the current flow.

Now, keeping your fingers pointed south, rotate your hand so you thumb points in the same direction as the current flow.

Out of palmPoints at southNegative electron flow

A current bearing wire is place between two bar magnets.What is the direction of the force on the wire?

We know that the magnetic field between the bar magnets is from the north pole to the south pole?

We also know that the current (electron flow) is out of the negative terminal, through the circuit and back to the positive terminal.

Your thumb points in direction if the negative current flow.

The force on the wire is shown by a vector coming out of your palm.

The force on the wire is shown by a vector coming out of your palm.

The force on the wire is shown by a vector coming out of your palm.