Electrostatic Pinwheel
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Electric Wind Once Again
Dear Reader, before diving into this topic, I kindly ask you to familiarize yourself with my short study on electric wind, available here. This is necessary because this article builds upon that text.
Getting to the Core of the Matter
The Franklin’s wheel, named after Benjamin Franklin, the American statesman and inventor, is a simple yet fascinating device. Among Franklin’s many contributions, he is also credited with inventing the lightning rod. This device is also known as an electrostatic pinwheel or a corona spinner.
Despite its simplicity, it serves as an excellent introduction to electrostatics, ionocrafts, and ion thrusters.
To build your own corona spinner, you only need a small steel washer and a rigid copper wire. The wire must be soldered to the washer and bent as shown in the image below:
All blades must be bent in the same direction and have well-sharpened tips. The rotor should then be placed on a base, consisting of a metal rod with a small indentation at the top, allowing it to spin freely. As a high-voltage source, you can use a Van de Graaff generator, a school electrostatic machine, or a ZVS high-voltage generator. For details on how to build a ZVS generator, I encourage interested readers to visit my page dedicated to this device. One of the secondary winding terminals of the generator is connected to the base of the pinwheel, while the other is grounded.
Warning: I do not recommend using a ZVS system for beginners without experience handling high voltage. The output of this device can reach several thousand volts (kV). Mishandling it can result in severe electric shock! The author assumes no responsibility for any damage or harm that may occur. Proceed at your own risk!
The assembled setup should look like this:
When power is applied, the pinwheel begins spinning rapidly, so it should be well-balanced.
In the video, we see the electrostatic pinwheel in action. Its operating principle is quite simple: an electrostatic wind is generated at the tips of the blades. Air is repelled from the sharp edges, and by reaction, the blades move in the opposite direction, causing the entire rotor to spin. At the tips of the blades, corona discharges also occur. These appear as a faint blue glow. A long-exposure photograph reveals the circular trails traced by the glowing blade tips.
Enjoy your experiments and have fun learning! :)
Further readings:
- Gębura G., Metodyka eksperymentu fizycznego w szkole podstawowej, PWN, Warszawa, 1978
- Griffiths D.J., Introduction to Electrodynamics, Prentice Hall, Nowy Jork, 1999
Marek Ples