This interesting device consists of a 1.5-inch ball with two small metal electrodes. When the two electrodes are touched simultaneously, the device flashes and makes a pleasing warbling sound. The Energy Ball utilizes a field effect transistor so even the slightest conduction between the two electrodes activates the Sphere. The Energy ball is completely self-contained and requires no additional batteries or energy source. It is often used to demonstrate closed and open circuits by having two students each touch a different electrode and then activate the device by holding hands. Totally cool!