The Faraday Flashlight
Among the latest gadgets is a battery-less flashlight called a Faraday flashlight. By shaking the flashlight back and forth, the user can generate enough electricity to enable an LED in the flashlight to glow.
In 1831, Michael Faraday discovered that moving a magnet through a coil of wire induces a current in the wire. The gadget that demonstrates this effect contains a magnet inside a hollow tube wrapped with wire. The wire is connected to a small circuit board that has a rectifier and a capacitor. With the help of the rectifier, the capacitor is charged with the same polarity on both the forward and backward motion of the magnet. The LED uses only a little current, so the charge stored in the capacitor can keep it shining for several minutes.
Copyright © 2006 Allen Watson III