Look at this battery, this bulb and these wires. What do you think has to happen for the bulb to light? Hands up your best guess, and say why you think that.

Remember those guesses: here is the idea we will test. The bulb often stays dark when the path from the battery is broken. A complete loop is a closed path with no gaps. We will build and watch for light versus dark next. Keep an eye out for breaks.

On the board is a circuit with a gap in it, and the bulb is dark.

Everything else is there: the battery, the wires, the bulb.

What is wrong, and what could go in that gap?

Before we close it, predict: what happens to the bulb when the gap closes? And what happens when it opens again?

In your group, build a circuit with a battery, bulb, switch and wires so the bulb lights when the switch is closed. This is the fiddly bit: most dark bulbs are just one loose clip, not a mystery. If it stays dark, check every join: is the loop complete? Does the switch need to be closed? When the bulb lights, you have seen a complete loop in action: a closed path from one end of the battery, through the parts, and back to the other end.

Your group chooses at least four materials from the tray. For each one, in this order:

1. Predict: light or no light? Say why.
2. Jot the prediction on your Investigation Journal page.
3. Place the material in the gap.
4. Note light or no light straight away, before you move on.