Electricity and Magnetism : AC - DC Generators / A Series/Parallel Circuit Puzzle / Circle of Magnetism / Dynamo 1/ Dynamo 2 / Induced Current - Eddy Currents / Lenz's Law / The Magnetic Field - Lines of Force / The Rotating Copper Disk / Pepsi Can / Helmholtz Coils / Electrons Beam
Dynamo 2

This exhibits shows how a magnetic field exerts a force on an electrical current. It also shows the direction of the force.

DO:

Push the button, this will start the power supply. Now take the insulated cable in your hand and make the fuzzy end  of the cable touch the copper disk lightly at point A.

SEE:

The disk will begin to rotate.

WHY?:   

- One pole of the power supply is connected to the center of the copper disc, the other pole is connected to the red cable with the fuzzy end. There is now an electrical current  I  flowing from the center of the disc O to point  A.

 -At point  A there is a magnetic field  B  provided by the large horseshoe magnet.

-The current experiences a force  F which is   perpendicular to both  the current  I and  the magnetic field  B; this  force makes the disc rotate.

The magnetic field produced by the horseshoe magnet  is strongest near the poles of the magnet and weaker farther away. You can explore this by touching the disc at various points on the disc, and observing the effects