Concepts

Magnetic levitation, key words ....

Overview

An elctromagnet levitates solid aluminum rings and causes them to 'jump' when the power is turned on suddenly. The physical property of the ring determines if and how high it will jump. A ring with the slit and a copper ring will not jump. A ring cooled in liquid nitrogen will jump higher than an identical ring that is at room temperature.

Details

Equipment

• [1] [location] An electromagnet
• [1] [location] Variac
• [1] [location] Set of rings (aluminum rings of varios diameters, one aluminum ring with a slit, and one copper ring)
• [1] [location] Forceps
• [1] [location] Small (~2L) dewar of liquid nitrogen
• Power bar (if necessary) 
• Extension cord (if necessary) 

Safety Equipment

• [1] [location] Safety goggles
• [1] [location] Safety gloves.

Classroom Assembly

1. Plase magnetic core on top of lecturn shelf. 
2. Variac can be on the shelf or on the lecturn.
3. Start with voltage at zero volts to begin.
4. Ensure a ring is being precooled in the dewar of LN2.
5. Confirm the demo works in the lecture hall!!!

Important Notes

• Ensure demo will not be place beneath low hanging lights or ceilling !!!

Script

1. Put on your safety goggles and gloves.
2. Place one of the two identical aluminum rings in the dewar of liquid nitrogen to cool.
3. Raise the electromagnet core so that it is about 75% above the frame and secure it in place using the set screw.
4. Plug the electromagnet into the variac.
5. Turn the variac to about 100V.
6. Place a ring on the electromagnet.
7. Turn on the variac. The ring will jump off the electromagnet.
8. Catch the ring.
9. Turn off the variac.
10. Repeat for a variety of rings including the identical aluminum ring cooled with liquid nitrogen. WEAR GLOVES when catching the liquid nitrogen cooled ring!

Additional Resources