Dropping Magnets

1
Dropping Magnets

• What will you observe when I drop this magnet
  onto this piece of copper? Incorporate all of
  your senses.

2
Dropping Magnets

• Take 3 minutes and write down an explanation for
  your observations.
• Now work with your group members to develop an
  explanation that you are all happy with.

3
Eddy Currents

• The dropping magnet causes a change in flux in
  the block of metal.
• What does a change in flux cause?
• EMF
• This emf causes currents to flow in the piece of
  metal which produces a field to oppose the change
  in flux.

4
Visual of Eddy Currents
5
Eddy Currents

• Pendulum
• What will happen when the pendulum moves through
  a magnetic field?
• http//www.kineticbooks.com/physics/17218/17247/sp
  .html

6
Applications of Eddy Currents

• Can you think of any applications of eddy
  currents?

7
Braking Systems

• http//www.cars.com/carsapp/national/?srvparsera
  ctdisplaytf/features/intercar/ic_index.tmpl
• Uses friction to slow things down
• In the process material is worn away.
• Eddy current disk demonstration.

8
Drawbacks of Eddy Currents

• Can you think of any drawbacks?
• Eddy currents consume energy!!!
• See transformer demonstration
• How do you solve this problem? http//www.kineticb
  ooks.com/physics/17218/17247/sp.html

9
Advanced Applications

• Use the measurement of eddy currents to find
  microscopic cracks in airplanes.

10
Eddy Currents

• Questions???