This Energy Ball is great fun and a great teaching tool as well. The one and a half inch white ball comes with two metal contacts on one side. When a person touches both contacts at the same time, completing the circuit, the ball lights up. When the ball lights up it releases an eerie siren as well. The Energy Ball can be a useful tool for teaching students about circuits, you can arrange large circles of students to complete the circuit, whereas everyone must be holding hands to activate the ball. If there is a break in the circuit, the ball turns off. You may also use the ball to demonstrate conductivity by showing what sort of materials will activate the ball. See if the ball will activate for someone with very dry hands.