The family has traveled to Knoxville, Tennessee for the last two weeks of July, and while we’re here we took the kids to the American Museum of Science and Energy in Oak Ridge. They have a nice display of high energy electrical phenomena, including a Jacobs Ladder, plasma ball, crackle tube, and Van De Graff generator.
The handsome young man in the picture is one of my sons, demonstrating a new high voltage hairstyle that he plans to take to school on the next “wacky hair day”. We can’t travel back to Oak Ridge just for that, so if he wants to repeat this hairstyle we’ll just have to build our own Van De Graff generator.
A Van de Graff generator consists of two terminals that collect opposite charges of static electricity. Charge is transferred from one end to the other by a belt of dielectric material, such as silk, that rotates around two pulleys. This mechanism is contained within the two terminals. The static charge can be provided by either a large DC potential applied to one terminal, or by using at least one pulley made from a non-conductive material that creates static electricity as it rubs against the belt — the same way a static charge is created on a balloon by rubbing it on your hair. By the way, if you read the above Wikipedia link to Van De Graff generators, you’ll find that creating static electricity by rubbing things together is called the triboelectric effect. You’ll also find that the English word “electricity” comes from the Greek word for amber, which generates static electricity when rubbed with wool, and is the first recorded example of generating electricity.
The DC powered generator is the one used in science labs due to it’s higher performance, while the non powered version is typically built by experimenters. A google search will turn up lots of plans for building Van de Graff generators:
Design News Gadgeteer, on assignment in Tennessee