Post on 24-Feb-2016
description
transcript
Click on a
Created byRichard J. Terwilliger
July 2001
around current bearing wires
Thumb points in the direction of electron flow.
Fingers curl around the wire in the direction of the
magnetic field.
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 flow
The 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 X
Out of the page is
shown by a dot
Into the page is shown by
an X
Out of the page is
shown by a dot
Into the page is shown by
an X
Out of the page is
shown by a dot
The current flow is now to the left
Grasp the wire with your hand
The current flow is now to the left
The 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 left
The 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 left
The 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.
Does the diagram at the right show the correct orientation of the magnetic field around the
current bearing wire?.
Is the diagram at the left correct?
The diagram is…
The diagram shows a compass placed above a
current bearing wire.
The compass needle points into the page
What is the direction of the current flow in the wire?
Click on your choice above.
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.
to determine the direction of the magnetic field.
We use the
Fingers curl in the direction of the magnetic field
The arrows show the
direction of electron flow.
Grab the loop with your
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
Several LOOPS of wire are called a
We also use the
to determine the magnetic field around a coil.
To demonstrate the
we’ll start by building an electromagnet.
To build an electromagnet or solenoid we start with a
cylinder.
We could use one of the cardboard rolls found at the center of toilet paper rolls
If the inside of the cylinder is hollow it is said to have
an air core.
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
Next attach a potential source
(battery)to the wire.
The current will flow from the negative
terminal
through the wire and back to the
positive terminal.
The current flowed up the back of the
coil
and down the front side or face of the
coil.
Current flowing through the coil creates a
magnetic field.
is used to determine the direction of the magnetic field.
The
The next few slides will show how to apply the
to this coil.
Grasp the coil with your left hand curling your fingers
around the coil in the direction
of electron flow.
Your thumb points to the
end of the coil
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
Use the
to determine the NORTH end of the coil.
Grab the coil with your
Your fingers will follow the electron flow.
Curl your fingers over the top and down the
back.
You thumb points to the
end of the coil.
We now know the
end of the coil.
and the
around the coil.
Let’s try another example.
We’ll start with another coil.
The coil is attached to a potential source but the
polarity is unknown.
We do know that
is on the bottom of the coil
AB
Using the
determine which is the negative terminal.
A B
AB
Grab the coil with your
so you thumb points
AB
Your fingers now curl in the direction of
AB
Your fingers now curl in the direction of
AB
B
The
must come from
AB
B
The
must come from
AB
Therefore is theB