One path or many?
In a single-path circuit, if one light breaks, everything stops. In a parallel circuit, each light has its own path, so if one light breaks, the others keep working.
Level 2 · Advance Leeuwenhoek · Ages 5–7
Traffic Lights
How do traffic lights work?
Build a mini city with its own traffic light. Lay a path of conductive tape, add red, yellow and green lights, connect the battery pack and switch on your street.
What children make
- A printed city template with roads and crossings
- Paths made of conductive tape
- Red, yellow and green LED lights
- A battery pack with an on/off switch
What you discover
- Red means stop, yellow means get ready to stop and green means go.
- Conductors like copper and iron let electricity flow. Insulators like paper, plastic, rubber and glass don't.
- A parallel circuit gives each light its own path.
- An LED has a long leg and a short leg, and the long leg goes to the positive side.
How it works
The science inside
Why all three glow
On your city card, all three lights glow at the same time because each one has its own path. Real traffic lights use a controller to switch them on one at a time.
Tape that conducts
Conductive tape has metal in it. It makes a flat road for electricity from the battery pack to each light and back.
Interactive exhibit
Try it: break one light
Break one light
Picture only: in real life, three LEDs in one path would need a bigger battery to light up.
S.A.M.'s safety tip
If a battery smells funny, smokes or gets very hot: stop, step away and tell a teacher straight away.
Watch before you build
Battery Safety with S.A.M.
Safety first · 0:32
Battery Safety with S.A.M.
Batteries power our projects, but some batteries are not safe to touch. S.A.M. explains what to look for and what to do.
- Never touch leaking, rusty, damaged or hot batteries
- Used batteries go in special collection bins
- Stop, step away and tell your teacher
Enquiries
Want to build this too?
Come and see what your child could build. Classes run in Rochedale, on Brisbane's southside. Send us a message and we'll help you find the right level.
