Electricity comes from moving electrons, or negative electric charges. Join Jared as he introduces the van de Graaf generator!
When the machine is turned on, the belt will move and rub against a piece of carpet at the bottom, picking up electrons. It brings the electrons up to the metal dome. Since electrons are negatively charged, they repel each other, and spread out on the dome.
When Jared touches the metal ball to the dome, electrons can move from the dome through the ball and wire back to the base, where they started. Electrons moving through this complete cycle create a current.
The animation in the following video illustrates how the van de Graaff generator works. Charge accumulates on the metal dome, creating an electric field.
Without the metal ball touching, negative charge builds up on the dome. Eventually the charge is strong enough that you’ll see purple sparks in the air! Those sparks are a plasma, where ionized air creates the current.
In the second video, Jared puts ribbon hair onto the van de Graaf generator! When charge builds up on the dome, now the electrons can spread out on the ribbons. The energy from the electrons repelling one another causes the ribbon hair to spike up!
Finally, Jared stacks pie tins onto the van de Graaf generator! This time when he turns the machine on, charges can spread out onto the pie tins! Eventually enough energy accumulates for the pie tins to fly off one by one.