--- title: "Light a bulb: a kitchen-table battery circuit" published: "2026-10-15" updated: "2026-10-15" author: "Dad Field Manual editors (drafted with AI help)" time: "45 min" cost: "About $15" ages: "7 to 12" where: "A clear table away from sinks and wall outlets, with a tray to keep small parts together." topics: ["indoor"] print: "https://dadfieldmanual.com/print?p=battery-circuit-lab" url: "https://dadfieldmanual.com/plans/battery-circuit-lab/" --- # Light a bulb: a kitchen-table battery circuit > Electricity feels like magic until your kid builds the loop that lights the bulb. In 45 minutes at the kitchen table you'll make a circuit, add a switch you build from a paper clip, and test which things in the junk drawer let the light come on. ## What you need - Two AA batteries and a 2-AA battery holder with wire leads (have / $5) - A small flashlight bulb (about 3 volts) in a mini screw-in holder ($5) - Three or four alligator-clip leads ($5) - Two brass paper fasteners, a metal paper clip and a scrap of cardboard (have) - Test objects: spoon, foil, a coin, pencil, eraser, plastic lid (have) - Electrical or masking tape (have) ## Before you start - **No button or coin batteries, ever.** A swallowed one can burn through a child's throat in as little as two hours. If you think one was swallowed, go to the ER now and call 1-800-222-1222. - **AA batteries only, never the wall.** This lab never touches outlets, extension cords or anything that plugs in. Say it out loud before you start. - **Keep the bulb in the loop.** A wire or metal object joining both battery ends with nothing between them can spark, smoke or start a fire. Feel something hot? Unclip it. - **You handle any wire stripping.** Clip leads mean no stripping. Afterward, take the batteries out and tape the ends of any you throw away. ## Steps 1. **Light the bulb** (Together) Put the batteries in the holder. Clip one lead from the holder to one side of the bulb holder and the other lead to the other side. The bulb lights. Say, "The electricity goes out one end, through the bulb and back in the other end. That loop is a circuit." 2. **Break the loop** (Kid) Ask, "What happens if I unclip one wire?" Let them guess, then unclip it. The light goes out. Clip it back on. Any gap anywhere in the loop stops the whole thing. 3. **Build a paper-clip switch** (Dad shows, Kid copies) Push two brass fasteners through the cardboard about an inch apart and spread their legs underneath. Hook a paper clip around one so it can swing over to touch the other. Clip the switch into the loop. Swing the clip to touch: light on. Swing it away: light off. 4. **Test what conducts** (Kid) Open the loop with two free clip ends and touch them to one object at a time, with the bulb still in the circuit. Before each one, ask, "Light or no light?" Sort the objects into two piles. Metal usually lights it; plastic, rubber and paper don't. 5. **Draw the circuit** (Kid) They draw the whole thing on paper: battery, wires, switch, bulb. Show them how a straight line is a wire and a circle with an X is a bulb. Ask them to trace the loop with a finger. 6. **Shut it down** (Together) Open the switch, unclip the leads and take the batteries out of the holder. Put everything in one bag or box, out of reach of any younger kids. ## If it stalls - If the bulb won't light, check that it's screwed in snugly and that each clip is biting bare metal. Then try fresh batteries. - If you use an LED instead of a bulb, it only works one way round. If it stays dark, swap its two wires. - If they lose interest, give them a mission: wire the switch so the light comes on when a shoebox lid opens. - If they ask about wall outlets, answer plainly: outlets carry far more power than AA batteries and are only for plugging things in, never for experiments. ## Variations - **Ages 7–8:** You clip, they predict and flip the switch. Stop after the switch and three or four test objects. - **Ages 9–10:** The full plan. Add a second bulb and compare one long loop with two bulbs side by side: which is brighter? - **Ages 11–12:** Swap the bulb for a small 3-volt hobby motor (about $3) with a paper flag taped to the shaft. Ask what happens if you flip the battery leads. ## Sources - **Button and coin battery danger.** CPSC says a swallowed button cell can burn through a child's throat or esophagus in as little as two hours, says not to let children play with or handle button or coin batteries, and says to seek medical attention immediately and call the National Battery Ingestion Hotline (800-498-8666) or Poison Help (800-222-1222). (checked 2026-10-15) - **Go to the ER right away.** The AAP says button and coin batteries can cause serious injury in a nose or ear and possibly death if swallowed, that they are found in remotes, toys and light-up shoes and clothing, and that a child who swallows one should be taken to an emergency room immediately. (checked 2026-10-15) - **Battery ends and metal.** New Hampshire's environmental agency says all batteries, even used ones, can carry a charge, that terminals touching each other or other metal can spark, smoke and possibly start a fire, and to tape the ends of alkaline AA, C, D and 9-volt batteries before throwing them away. (checked 2026-10-15)