Electrostatic Discharge
Electrostatic discharge is the spark that jumps when built-up static charge moves from one thing to another.
Static builds up in a wool sweater the same way charge builds up on two objects that rub together. Picture a glass jar full of tiny dots packed tight on one side, and an empty tray sitting close by. When enough dots crowd the jar, a bright spark jumps across the gap to the tray. That spark is the charge rushing to even out between the two objects.
Explaining electrostatic discharge by grade level
Rub a wool sock on a foam plate. The rubbing pulls tiny charges off the sock and onto the foam. Now bring the foam near a metal pie pan. A small spark jumps from the foam to the pan. That spark is the charge moving all at once.
Projects that explore electrostatic discharge
Electrostatic discharge does not always happen as a single spark — it can repeat in a rapid cycle. When a charged soda can repels a metal tab toward a grounded can, the tab dumps its built-up charge on contact and swings back to collect more. This back-and-forth cycle repeats several times per second, and occasional sparks snap between the cans as the charge jumps across the gap.
A huge buildup of electric charge causes lightning when it jumps between clouds and the ground. You can trigger that same discharge on a small scale. Rubbing styrofoam quickly with a wool sock creates a negative charge that repels electrons on the pie plate. Turn out the lights and slowly bring your finger close to the pie plate. A small spark jumps from the plate to your fingertip, one you can see and hear.