For you to do
You'll build a 'voltaic pile' — a stack of coin / salty-paper / foil sandwiches. Each sandwich is one weak battery; stacked together they can light an LED.
Grown-up help
Ask a grown-up to help you find a suitable LED and to check your stack before you connect it. One quick check-in, then you run it.
Build the pile
Stop and check
Only ever use a single LED and this coin pile. Never connect wires to a wall outlet or a real battery pack for this — the pile is safe because it's weak.
- Soak squares of paper towel in very salty water.
- Make sandwiches: coin → salty paper → foil. Stack 6–8 of them in the same order.
- Touch the LED's two legs to the top coin and the bottom foil. Try flipping the LED legs if it doesn't light.
What's happening
Two different metals (copper and aluminum) sitting in salty water push electric charge in one direction — that's a **battery**. Stacking cells adds their push together until it's enough to light the **LED**. The metals and foil are **conductors** that complete the **circuit**.