How To Determine the Shape of Raindrops Through Experimentation Project

Here's How:

1. Print out the diagram of the raindrop machine.
2. Gather the materials listed at the bottom of this article. Note that a hair dryer can substitute for the vaccuum.
3. Attach the PVC pipe or other plastic tubing to the vacuum fan. Add a series of screens to the inside of the pipe and attach it with wires. The screen apparatus should be made to allow air to flow through, but water should not be able to enter into the electrical equipment. A downward sloping screen with solid material around the center may work well.
4. Plug the vacuum into a variable transformer. A variable transformer is designed to control the amount of energy that will flow to your vacuum cleaner or hair dryer via a knob or dial that controls the energy flow. Also known as a variac, this may be the more expensive part of the experiment. Sources for getting a variable transformer are listed at the bottom of this page.
5. If you cannot obtain a variable transformer, using multiple heights to suspend a water drop with a hair dryer might work. Extreme care should be taken to reduce the risks of electrical shock hazards. This experiment should not be attempted by young people or students without direct adult supervision and assistance.
6. Keep in mind that the cord for the electrical equipment should have a “drip loop” that would prevent water from entering an electrical outlet if it splashes or falls on the cord. A drip loop is when the slack on an electrical cord is lower than the plug as shown in the diagram.
7. Once constructed, use a water dropper to suspend a drop over the apparatus. Again, care should be taken to avoid letting the water drop enter into the electrical machinery. The idea is to get a water drop suspended in the flowing air. It may take some experimentation with the energy in the air flow to get the water drop to stay suspended.
8. Take photographs of the water drop if desired and record your results.

Tips:

1. Warning!This experiment is not designed for students to complete without direct adult supercision. Electrical hazards are a concern!
2. Teachers: Set up this raindrop demonstration in a physics, earth science, or weather science class and students will be impressed!
3. Advanced: Categorizing raindrops by initial size and determining wind velocity are excellent ways to make this project even more advanced. Using physics equations for force, mass, acceleration, and drag should yield excellent results. Another suggestion might be to add some smoke to the air flow to see the drag.
4. References: Adapted from an original education activity from the National Oceanographic and Atmospheric Administration - National Weather Service.

What You Need:

• Plastic tubing
• Vacuum cleaner fan (or hair dryer)
• Screen
• Plastic PVC pipe approximately 6 inches high
• Small diameter wire
• Water dropper
• Variable transformer