The Wimshurst machine: better than the Van De Graaff
The Wimshurst machine is a device for creating static charge, created in 1880 by James Wimshurst. By using a unique combination of brushes, metal plates, and Leyden jars (early capacitors), this early influence machine can create a static electric charge using the property of induction. In a similar class of machines is the Van De Graaff generator, the more famous cousin of the Wimshurst machine, known for its distinctive metal dome. In a Van De Graaff generator, a powered belt rubs across brushes in the dome to make static electricity. This machine is used around the world to teach kids about the properties of static electricity and current/voltage, but I believe that as a teaching tool it is not very effective. Teachers everywhere should instead use the Wimshurst machine to teach about static electricity, rather than the Van de Graaff.
In a Wimshurst, charge is created by turning a hand crank on the back of the machine. When one turns the handle, they can see the two disks start to move, and can tell the brushes are rubbing across the metal sectors. All of the wiring to the Leyden jars and to the terminals are clearly visible and easy to understand. In contrast, the Van de Graaff was created to produce higher voltages more quickly, and so therefore it uses electricity to power its motor. Contained within the top dome are the same basic components to produce a charge, but unlike the Wimshurst, they are not visible.
The Van de Graaff is a staple of museums and science classrooms nationwide, but I don’t believe it is effective at teaching the principles behind it. If more teachers started using a Wimshurst machine to show induction, conduction, static, voltage, etc. then it would be easier for children to understand, due to the hands-on and easily visible components of this machine.