3D40.30 – Chladni Plates

Description: Demonstrates standing waves in two dimensions on a plate

Equipment

  • Square Chladni Plate
  • Function Generator
  • Mechanical Vibrator
  • Frequency List
  • Fine Sand

Demonstration Procedure:

  1. Important: Set the switch to the mechanical vibrator to the locked position; attaching and removing the plate while the vibrator is unlocked could damage the vibrator.
  2. Connect the Chladni plate to the mechanical vibrator, and then the mechanical vibrator to the function generator.
  3. Unlock the mechanical vibrator
  4. Power on the function generator.
  5. Press the Output Standby button on the function generator, and set the frequency and voltage to one of the recommended settings on the frequency list
  6. Pour sand on top of the plate.
  7. Press the Output Standby button again; the plate should start vibrating and a pattern should appear on the plate
  8. When finished, press the power button to turn off the function generator; the plate should stop vibrating.

Tips:

  • This demonstration can get a bit messy with the sand; putting the vibrator inside a shallow box to catch the sand vibrating off is recommended
  • At certain frequencies, the plate can be quite loud, and the high frequencies are high pitched as well.
  • Feel free to adjust the frequencies and voltages, but watch the screen as you do so, and be careful not to set the function generator to overcurrent, as it may damage the hardware.

Concept: When you vibrate a string, a standing wave is created on the string, and you can see the areas of the string that move a lot, the peaks and the troughs, and you see areas that don’t move at all, the nodes. When you vibrate the Chladni plate, you create a standing wave on the plate as well. However, the standing wave on the plate is in two dimensions, with more complicated boundary conditions on the waves depending on the shape of the plate. Similarly to the string, there are areas of the plate that vibrate a lot, and areas that don’t vibrate at all, resulting with the sand on top of the plate moving off of the areas that vibrate a lot into areas that don’t vibrate at all.

28-J2