BrightKidz Library
Subjects
A closed circuit lighting a bulb A loop of wire drawn as a rectangle. A battery sits in the bottom wire and a light bulb sits in the top wire, with short rays coming off the bulb to show it is lit. The loop has no gap anywhere in it, which is why the electricity can go all the way round and back into the battery.

Let's Build a Light-Up Circuit

About 4 minutes

Electricity will not travel along a wire that stops in mid-air. It has to go all the way round a loop: out of the battery, through the bulb, and back into the battery again. Close that loop and the bulb lights. Leave one gap anywhere in it and nothing happens at all. Here is how to build one.

What You'll Need

Gather these things. Ask a grown-up to help you find them.

How to Build It

Follow these steps in order. Each one adds another piece of the loop.

  1. Get Connected: If you have holders, put the battery in its holder and the bulb in its holder. If not, just hold the battery and bulb.
  2. Make a Loop: Take one wire and touch one end to the metal part (the bottom or side) of the battery.
  3. Another Connection: Now, take the other end of that wire and touch it to one of the metal parts of the light bulb (the bottom or the side).
  4. The Final Touch: Take the second wire. Touch one end to the other metal part of the light bulb.
  5. Close the Loop: Touch the other end of the second wire to the other metal part of the battery. That last touch finishes the loop, and the bulb should light.

Troubleshooting and Tips

If your bulb does not light, work through these one at a time:

The loop you just closed is called a circuit. Lift one wire off the battery and the bulb goes out at once, because the electricity has nowhere left to travel.

Try It: Close the Loop

A battery, a bulb and some wire on a grid, with gaps left in the wire. Put a piece of wire in a gap and the bulb lights the moment the loop is finished — not one moment before. A wire that stops in mid-air does nothing, however close it gets to the bulb. Later on there are two bulbs, and the job is to put one of them out without taking away a single piece of the wire that touches it.