Standing wave machines are fun to make because they are easy to build and amazing to watch! Here’s a simple one you can make on your own using the materials from the previous lessons in electricity.
[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Materials:
- AA batteries (4, cheap “dollar-store” carbon-zinc kind work great)
- AA battery case (4)
- Alligator clip leads
- DC, 3V motor (2)
- Hot glue gun (and glue sticks)
- Masking tape
- Popsicle sticks
- String
- Scissors
How many wavelengths can you see in yours? Where are the nodes and antinodes? Change the tension in the strong to get different harmonics to show up! (Note – if you know how to change the motor speed using a potentiometer, you can do that also!)
Also note – if you’re finding that the string wads into a tight ball after only a few seconds, it means that one of your motors is going the wrong direction. Stop both motors and switch the wires in the back of ONE of the motors to reverse the polarity (plus and minus) so the motor spins in the opposite direction. You want the one motor to wind up the string and the other to un-wind it at the same time. Eventually, since the motors spin at slightly different speeds, the string will get wound up and you’ll need a new piece of string.
Click here to go to next lesson on Standing Wave Math.
[/am4show]