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Left Hand Rules. by Richard J. Terwilliger. Left Hand Rule. st. Left Hand Rule. 1. Left Hand Rule. B. Click on a. i. N. LEFT HAND RULE. S. rd. 3. nd. 2. F. Left Hand Rules. Created by Richard J. Terwilliger July 2001. Left Hand Rule. st. Left Hand Rule. 1. Left Hand Rule.

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Left hand rules

Left Hand Rules

by

Richard J. Terwilliger


Left hand rules

Left Hand Rule

st

Left Hand Rule

1

Left Hand Rule

B

Click on a

i

N

LEFT HAND RULE

S

rd

3

nd

2

F

Left Hand Rules

Created by

Richard J. Terwilliger

July 2001


Left hand rules

Left Hand Rule

st

Left Hand Rule

1

Left Hand Rule

B

i

N

S

rd

3

nd

2

F

Left Hand Rules


Left hand rules

st

1

Left Hand Rule

e

e

e

e

e

e

Magnetic Fields

around current bearing wires


Left hand rules

st

1

Left Hand Rule

e

e

e

e

e

e

Thumb points in the direction of electron flow.

Fingers curl around the wire in the direction of the magnetic field.


Left hand rules

N

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


Left hand rules

N

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


Left hand rules

N

The magnetic field above the wire points into the page.


Left hand rules

N

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


Left hand rules

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






Left hand rules

Out of the page out of the page is shown by a dot

X

Into the page is shown by an X


Left hand rules

X out of the page

Out of the page is shown by a dot

X

Into the page is shown by an X

X


Left hand rules

X out of the page

Out of the page is shown by a dot

X

Into the page is shown by an X

X


Left hand rules

e out of the page

e

e

e

e

e

LEFT

Grasp the wire with your hand

The current flow is now to the left


Left hand rules

e out of the page

e

e

e

e

e

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.


Left hand rules

e out of the page

e

e

e

e

e

X

X

X

X

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.


Left hand rules

e out of the page

e

e

e

e

e

The current flow is now to the left

X

X

X

X

The thumb points in the direction of electron flow,

the fingers curl around the wire in the direction of the magnetic field.


Left hand rules

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.


Left hand rules

Does the diagram at the right show the correct orientation of the magnetic field around the current bearing wire?.

CORRECT

WRONG


Left hand rules

? of the magnetic field around the current bearing wire?.

CORRECT

WRONG

Is the diagram at the left correct?

X

X

X

X

X

X

The diagram is…


Left hand rules

The diagram shows a of the magnetic field around the current bearing wire?.compass placed above a current bearingwire.

compass


Left hand rules

The compass needle points of the magnetic field around the current bearing wire?.into the page


Left hand rules

What is the direction of the current flow in the wire? of the magnetic field around the current bearing wire?.

East

West

Click on your choice above.


Left hand rules

Left Hand Rule of the magnetic field around the current bearing wire?.

nd

2


Left hand rules

Loops of the magnetic field around the current bearing wire?.

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


Left hand rules

negative of the magnetic field around the current bearing wire?.

Loops

The electrons flow from the negative terminal of the battery


Left hand rules

positive of the magnetic field around the current bearing wire?.

Loops

through the wire and back to the positive terminal.


Left hand rules

Loops of the magnetic field around the current bearing wire?.

through the wire and back to the positive terminal.


Left hand rules

Loops of the magnetic field around the current bearing wire?.

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


Left hand rules

We use the of the magnetic field around the current bearing wire?.

Left Hand Rule

to determine the direction of the magnetic field.

nd

2

Loops


Left hand rules

Left Hand Rule of the magnetic field around the current bearing wire?.

nd

2

for

Loops

Coils

and

The arrows show the direction of electron flow.

Fingers curl in the direction of the magnetic field


Left hand rules

Grab the loop with your of the magnetic field around the current bearing wire?.

Left Hand Rule

LEFT HAND

nd

2

for

Loops

Coils

and


Left hand rules

Left Hand Rule of the magnetic field around the current bearing wire?.

nd

2

for

Loops

Coils

and

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


Left hand rules

Left Hand Rule of the magnetic field around the current bearing wire?.

nd

2

for

Loops

Coils

and

Your thumb now points

S

NORTH

N


Left hand rules

S of the magnetic field around the current bearing wire?.

N

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


Left hand rules

S of the magnetic field around the current bearing wire?.

N

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


Left hand rules

N of the magnetic field around the current bearing wire?.

S

N

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


Left hand rules

N of the magnetic field around the current bearing wire?.

N

N

S

N

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


Left hand rules

I’m back! of the magnetic field around the current bearing wire?.


Left hand rules

Several LOOPS of wire are called a of the magnetic field around the current bearing wire?.

Coil

Coils


Left hand rules

We also use the of the magnetic field around the current bearing wire?.

Left Hand Rule

to determine the magnetic field around a coil.

nd

2

Coils


Left hand rules

To demonstrate the of the magnetic field around the current bearing wire?.

Left Hand Rule

we’ll start by building an electromagnet.

nd

2

Coils


Left hand rules

To build an of the magnetic field around the current bearing wire?.electromagnet or solenoid we start with a cylinder.

Coils




Left hand rules

The front side of the coil is called the an faceof the coil.

FACE

Air Core



Left hand rules

Each wrap is a wire around loop of wire.



Left hand rules

Next attach a potential source wire around

(battery)

to the wire.





Left hand rules

and wire around down the front side or face of the coil.



Left hand rules

The wire around

Left Hand Rule

is used to determine the direction of the magnetic field.

nd

2


Left hand rules

The next few slides will show how to apply the wire around

Left Hand Rule

to this coil.

nd

2


Left hand rules

Left Hand Rule wire around

nd

Your thumb points to the end of the coil

2

NORTH

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

N

for loops and coils


Left hand rules

Left Hand Rule wire around

nd

2

S

N

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

for loops and coils


Left hand rules

? wire around

S

N

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


Left hand rules

S wire around

N

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


Left hand rules

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





Left hand rules

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




Left hand rules

Use the over the top and down the back

Left Hand Rule

to determine the NORTH end of the coil.

nd

2


Left hand rules

Grab the coil with your over the top and down the back

Left Hand


Left hand rules

Your fingers will follow over the top and down the backthe electron flow.


Left hand rules

Curl your fingers over over the top and down the backthe top and down the back.


Left hand rules

You thumb points to the over the top and down the back

NORTH

end of the coil.

N


Left hand rules

We now know the over the top and down the back

SOUTH

end of the coil.

S

N


Left hand rules

and the over the top and down the back

MAGNETIC FIELD LINES

around the coil.

S

N


Left hand rules

Let’s try another example. over the top and down the back


Left hand rules

We’ll start with another coil. over the top and down the back


Left hand rules

? over the top and down the back

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


Left hand rules

We do know that over the top and down the back

NORTH

is on the bottom of the coil

?

NORTH


Left hand rules

Using the over the top and down the back

Left Hand Rule

determine which is the negative terminal.

A

or

B

?

nd

2

A

B

NORTH


Left hand rules

Grab the coil with your over the top and down the back

Left Hand

so you thumb points

NORTH

?

A

B

NORTH


Left hand rules

Your fingers now curl in the direction of over the top and down the back

Electron flow

?

A

B

NORTH


Left hand rules

Your fingers now curl in the direction of over the top and down the back

Electron flow

?

A

B

NORTH


Left hand rules

The over the top and down the back

Electrons

must come from

B

?

A

B

NORTH


Left hand rules

The over the top and down the back

Electrons

must come from

B

?

A

B

NORTH


Left hand rules

Therefore is the over the top and down the back

NEGATIVE TERMINAL

B

?

A

B

NORTH


Left hand rules

Left Hand Rule over the top and down the back

B

i

N

S

rd

3

F


Left hand rules

Left Hand Rule over the top and down the back

rd

3

Now the


Left hand rules

There are 3 parts over the top and down the backto the

3 parts

3

Left Hand Rule

rd

3


Left hand rules

one over the top and down the back

An external magnetic field.

rd

3

Left Hand Rule


Left hand rules

NORTH over the top and down the back

SOUTH

to

rd

3

Remember that the magnetic field goes from

Left Hand Rule


Left hand rules

two over the top and down the back

Either a charge moving across the magnetic field.

rd

3

Left Hand Rule


Left hand rules

rd over the top and down the back

3

two

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

Left Hand Rule


Left hand rules

three over the top and down the back

Force

A force acting on the moving charge or current bearing wire.

rd

3

Left Hand Rule


Left hand rules

rd over the top and down the back

3

I will now show you how to apply the

Left Hand Rule


Left hand rules

SOUTH over the top and down the back

SOUTH

Point your fingers


Left hand rules

Or the same direction over the top and down the backas the

MAGNETIC FIELD

SOUTH


Left hand rules

Your thumb points in the direction of negative over the top and down the back

CURRENT FLOW

-i

SOUTH


Left hand rules

And the over the top and down the back

FORCE

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

-i

SOUTH

FORCE


Left hand rules

rd over the top and down the back

3

Let's try it with our example

Left Hand Rule


Left hand rules

rd over the top and down the back

3

First point your fingers of your left hand

SOUTH

Left Hand Rule


Left hand rules

Notice that your fingers over the top and down the backpoint in the same direction as the magnetic field shown by the symbol

rd

3

B

B

Left Hand Rule


Left hand rules

Your thumb points in the direction over the top and down the backof negative current flow

-i

rd

3

-i

B

Left Hand Rule


Left hand rules

Force over the top and down the back

rd

3

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

-i

B

Left Hand Rule


Left hand rules

Force over the top and down the back

rd

3

So the force acting on the wire is

UP

-i

B

Left Hand Rule


Left hand rules

rd over the top and down the back

3

Let’s try another example

Left Hand Rule


Left hand rules

N over the top and down the back

S

rd

3

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

Left Hand Rule


Left hand rules

N over the top and down the back

rd

3

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

S

Left Hand Rule


Left hand rules

Left Hand Rule over the top and down the back

N

rd

rd

3

3

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

S

Left Hand Rule


Left hand rules

N over the top and down the back

rd

3

Using your left hand point your fingers

SOUTH

S

Left Hand Rule


Left hand rules

N over the top and down the back

rd

3

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

S

Left Hand Rule


Left hand rules

N over the top and down the back

rd

3

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

S

Left Hand Rule


Left hand rules

The force on this section of wire is over the top and down the backout of your palm or

DOWN

N

rd

3

S

Force

Left Hand Rule


Left hand rules

N over the top and down the back

Current Flow

Magnetic Field

Negative electron flow

Points at south

S

Force

Out of palm


Left hand rules

N over the top and down the back

S

N

S

A current bearing wire is place between two bar magnets.

What is the direction of the force on the wire?


Left hand rules

N over the top and down the back

S

N

S

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


Left hand rules

N over the top and down the back

S

N

S

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


Left hand rules

Therefore the current flow in the section of wire between the bar magnets is toward the top of the page.

N

S

N

S


Left hand rules

We can now use the the bar magnets is toward the

rd

Left Hand Rule

3

to find the direction of the force on the wire.

N

S

N

S


Left hand rules

Point the fingers of your the bar magnets is toward the

Left Hand

in the direction of the magnetic field, south.

N

S

Fingers point south

N

S


Left hand rules

current flow the bar magnets is toward the

N

S

Fingers point south

N

S

Your thumb points in direction if the negative current flow.


Left hand rules

current flow the bar magnets is toward the

Force on wire

N

S

Fingers point south

N

S

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


Left hand rules

Force on wire the bar magnets is toward the

N

S

N

S

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


Left hand rules

Force on wire the bar magnets is toward the

N

S

N

S

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


Left hand rules

Have fun using the the bar magnets is toward the

Left Hand Rule

rd

3