1) A conductor moving through a magnetic field will induce an electromotive force (EMF) in the conductor.
2) As the electrons in the conductor are forced to one side by the magnetic field, it creates a potential difference between the ends of the conductor.
3) According to the law of conservation of energy, the induced current will flow in the opposite direction of the motion that created it, generating a force opposing the original motion as predicted by Fleming's left-hand rule.
2. Describing the Inducing of EMF – learn these steps
1. Conductor moving in a magnetic field
If a conductor moves at a speed v through a magnetic field, the
electrons inside it receive a force due to their Motion in the Magnetic
field.
Remember that
electrons moving
downwards are like
current flowing
upwards.
Use Fleming’s Left
Hand Rule to predict
which way they will
move
The electrons move towards the left side of the conductor shown in
this picture.
3. Describing the Inducing of EMF – learn these steps
2. An Induced EMF is created
Because the Charges are
separated it creates a
Potential Difference
between the two ends.
The Charges would ‘like’
to move back but can’t
because of the Magnetic
Field and the Motion of
the conductor which are
combining to move them
apart.
If an external circuit is connected they will flow through it to get to
the lower potential.
4. Describing the Inducing of EMF – learn these steps
3. Conservation of Energy
Fleming’s Left-Hand
The current that flows makes Rule force created by
it’s own force on the the Current
conductor.
You can use Fleming’s Left
Hand Rule to predict it too.
This force is in the opposite
direction to the motion that Force creating
is creating the current! the Motion
If there wasn’t an opposing Force being made then once you
started pushing the Conductor through the field it would
carry on making current for ever with no more force needed.
This would contradict the Law of Conservation of Energy
5. Describing the Inducing of EMF – learn these steps
4. Calculating the Induced EMF
Force on charge in B-Field
This is known as the
Induced EMF
Electric Field Strength Definition
6. Flux Density (B) & Flux (Φ)
Magnetic Flux Density (B)
This is just a measure of the closeness
of the field lines, or the field lines per
unit area
Flux (Φ)
This is the sum of all the flux density
(field lines per unit area) in an Area.
Φ=BA
Most people find the idea of Flux Φ really hard to understand
8. Faraday’s Law
Faraday’s Law just puts all of these ideas in one simple
equation:
emf = Rate of Change of flux
Sometimes an E or Ԑis used for EMF
9. Faraday’s Law Simulations
Faraday’s Law on PhET
http://phet.colorado.edu/en/simulation http://phet.colorado.edu/en/simulation/farada
/faraday ys-law
Use these to help you understand the ideas behind Faraday’s Law
10. Extra Facts 1: Fleming’s Right Hand Rule
Fleming’s Right Hand Rule gives the direction of the Induced (made) Current
if we know the Motion and the Field.
