3B30.30 Buzzer in a Bell Jar

Concepts

Air as the medium for sound waves

Overview

A buzzer goes from loud to almost inaudible when placed in a vacuum chamber which has its air pumped out.

Details

Equipment

  • [1] Pump
  • [1] Bell jar
  • [1] Buzzer
  • [1] Hook
  • [1] Duct tape
  • [1] Power bar 
  • [1] Extension cord

Classroom Assembly

  1. Tape the hook to the top of the bell jar.
  2. Position the bell jar where students can see it.
  3. Place the pump nearby, plugged into a power bar for an on-off switch.
  4. Arrange the buzzer's strap for easy hanging on the hook.

Script

  1. Twist the buzzer wires together once to activate.
  2. Hang the buzzer inside the bell jar.
  3. Connect the hose from the pump to the bell jar.
  4. Activate the pump. The buzzer should become nearly inaudible, even from up close.
  5. Turn off the pump.
  6. Disconnect the hose to let air back in. The buzzer should become highly audible again.
  7. Separate the buzzer wires.

 

Additional Resources

References

  • PIRA 3B30.30

Disclaimer

  • Don't attempt this at home!

Last revised

  • 2017

Technicals

Related AV

Related demos

  • ?

 

If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.