Physics Dept. Demonstration Manual

DEM26 - Forever Spin


To demonstrate a magnetic field inducing a current in a coil.

  • Base and Spinning Top


?Forever Spin" consists of a spinning top with a radially oriented magnetic field and an associated base that houses a conductive coil. When the top spins past the center of the base, its changing magnetic field induces a current in the coil which momentarily opens the switch to the battery resulting in powering up the electromagnet. The electromagnet then delivers enough torque to the spinning top to allow it to speed up and spin away from the center. Since the electromagnet is only engaged when the top crosses near the center of the base, the battery can last for over a week of continual use!

Thanks to Pam for bringing the Forever Spin in for us to use.