Purpose: To show the effect of currents induced in conductors near the iron core of an electromagnet excited by 60 cycle A.C.

Place an aluminum ring over the long end of the rectangular core of the solenoid and press the button on the control box. The ring will be thrown into the air. Variations include:

1. Use of a ring of lower conductivity.
2. Use of ring with gap.
3. Place the ring over short end of the rectangular core to demonstrate that a magnetic field gradient is necessary to produce a force.
4. Cool the metal rings with liquid nitrogen and get spectacular results.
5. Gently place one of the disk-shaped rings over the vertical core and let it levitate while the magnet is excited.
6. Push the LN₂-cooled ring downward near the coils and notice that the ring quickly heats.
7. Place the coil with bulb attached over the core and note the variation in bulb brightness with position of the coil.
8. Notice that when the removable section of the core is rested across the U-shaped part to close the magnetic circuit, it can be easily removed. Once the magnet is energized, it is very difficult to remove this section because of the residual magnetism.
9. See how to get liquid nitrogen.

References: