Start By:

  1. Pushing the Yellow button to start the power supply.
  2. Take the Orange insulated cable in your hand and make the fuzzy end touch the copper disk lightly as seen in the above photo.

What happens to the copper disk?

Answer: The disk begins to rotate!


When the cable is touching the copper disk, an electrical current I flows from the center of the disk through the copper to the cable.


The large horseshoe magnet provides a magnetic field B perpendicular to the surface of the disk.

The Lorentz force law says current traveling through a magnetic field experiences a force, F, perpendicular to the direction of the current flow and to the direction of the magnetic field.

So, the disk experiences a force F that is perpendicular to both the current I and the magnetic field B; this force makes the disk rotate!


Physics Lecture Demonstration Database


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