Build yours at home · Build 004
What lets electricity through?
What we're doing
Use the play-dough loop from the first lessons, with one gap in it. Push things across the gap. If the light comes on, that thing lets electricity through.
About 15 minutes.
Goes with these lessons
Get these parts
- The play-dough setup: 4×AA battery holder, an LED and Play-Doh LED (Elegoo kit); holder (electronics shop or online); Play-Doh (household)
- Things to test: a metal spoon or key, a coin, a strip of foil, a pencil sharpened at both ends, a plastic straw, a wooden craft stick, a rubber band (household)
Fill each holder with the matching number of AA batteries (household).
Keep it safe
Battery power only, never household power. Use AA packs matched to the parts, not a 9V battery. A grown-up connects and disconnects the pack. Stop immediately if any part warms. Never join the pack's two metal ends: the wires can get hot. Coin cells stay with grown-ups, locked away. CPSC warns a swallowed button or coin cell can burn through a child's throat in about two hours; suspected swallowing needs emergency medical care immediately.
Test only loose, dry things. Never test a plug, socket or anything plugged in.
Steps
- 1
Make three balls of dough in a row, a finger apart. Push the battery's red wire into the left ball and the black wire into the right ball.
- 2
Push the LED's long leg into the left ball and its short leg into the middle ball. Switch on. No light yet: there's a gap between the middle and right balls.
- 3
Push a metal key into the middle and right balls so it joins them. The light comes on! Metal lets electricity through.
Not working? Check the LED's long leg is in the red-wire ball.
- 4
Try each thing on your tray. Guess first, then test. Sort them into two piles: lights it, doesn't.
- 5
Try the pencil. Its lead lets a little through, so the light may be dim.
- 6
Switch off, take the wires out and put the dough away.
Talk while you build
- Which material do you think will let the light shine?
- What stayed the same when we changed the sample?
Spot it at home
- Plugs and cables: metal pins, plastic covers. The plastic handle on a screwdriver.
Why is the outside of this cable plastic?
More for grown-ups · printed parts
Optional equipment
Prints that make the build easier. None are required. Every build works with tape and clips.
Jefferson Lab
We couldn't find a printable tester, so this wooden one is the template for the first part we design ourselves.
Not printed yet
Grown-up references
Thomas Edison for Kids · Laurie Carlson Edison's story with activities, including testing circuits, switches and materials.