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This text is meant to accompany class discussions. It is not everything there is to know about uniform circular motion. It is meant as a  prep for class. More detailed notes and examples are given in the class notes, presentations, and demonstrations. See the links below.
Click for the questions that go with this reading

Thanks to the movie Back to the Future, you have probably heard of "flux" when Dr. Brown discusses the "flux capacitor with Marty.

Sadly, the flux capacitor is not real. But "flux" and "capacitors" are real.

"Flux" is the product of the amount of magnetic field going though an area times the cross sectional area.

The symbol for magnetic flux is the Greek letter "phi" with the subscript "B," ΦB. The equation for flux is

B: magnetic field measured in Tesla's [T]
A: cross sectional area measured in m2.
ΦB: flux measured in Webers [Wb] Note Wb = T•m2.
θ: acute angle between the magnetic field's direction and the area vector.

The area vector is drawn in the geometric center of an object and is perpendicular to the plane of the area. It's length represents the area of the surface.

Lenz's Law states that when the flux is changed, charges will move to counter the change in flux.

This video can be found on YouTube at



What direction is the current flowing across the resistor on the left when the switch on the right is closed?


Paste video frame here.




A magnet is dropped through the hoop shown below. Make a graph of the current versus time as the magnet enters, travels through, and leaves the hoop. Also decribe what the current does through the resistor on the hoop.


Paste video frame here.



  • Question 1
  • Question 2
  • Question 3
  • Question 4
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by Tony Wayne ...(If you are a teacher, please feel free to use these resources in your teaching.)