A part that stores electricity

Ask while they play

What did the light do when you unplugged the battery? Where did that electricity come from?

Spot it at home

• Unplug a phone charger or power strip that has a little light. Does the light fade instead of going out at once? A camera flash fills up, then lets it all out in one bright burst.
• Almost every gadget with a plug or battery has capacitors on its board: chargers, speakers, remote controls.

Where did the light's electricity come from after we unplugged it?

How it helps a robot

• When a motor starts, it gulps electricity all at once. A capacitor near the brain covers that gulp, so the brain doesn't restart.
• It smooths out bumpy power, so sensors give steady numbers.
• A robot can keep a light or a memory going for a moment if a battery wire wiggles loose.

Talk about it later

Where else could a stored burst help?