Concepts

Damped harmonic oscillator, eddy currents

Overview

A strong permanent magnet acts as a simple pendulum, swinging back and forth while hanging from strings. A copper plate underneath the magnet can be moved up to tune the eddy current damping.

Details

Equipment

• [1] Magnet on strings
  
• [1] Copper plate on a wooden block
  
• [1] Lab jack
  
• [1] Lab stand
  
• [1] 90-degree clamp
  
• [1] Aluminum rod
  

Classroom Assembly

1. Clamp rod to lab stand.
2. Hang magnet on rod.
   

Important Notes

• Danger! Strong magnets may disrupt pacemakers!
• Strong magnets can pinch fingers.
  
• Strong magnets may erase magnetic memory and magnetic stripes on credit cards.

Script

1. Swing the magnet to show the undamped motion.
2. Place the lab jack and copper plate under the magnet.
3. Swing the magnet to show the damped motion.
4. Adjust the lab jack height for a different level of damping and repeat.
   

Additional Resources