BuilderGrades 4–8⏱ 15 min
Simple circuits
Connect batteries and bulbs, test what conducts electricity, and compare series with parallel.
Standards: 4-PS3-24-PS3-4
1Wonder
When you flip a light switch, the light comes on instantly. What is actually happening inside the wires, and why does a switch stop it?
2Explore
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💡 The circuit is complete: the bulbs light up! Voltage 1.5 V Current 0.5 A
Batteries
Bulbs
Bulbs connected
In the gap
Try this
- Turn the switch off and on. What happens to the moving dots?
- Put each object in the gap. Which ones let the bulb light up?
- Add a second battery. Is the bulb brighter?
- Add more bulbs in a row (series), then side by side (parallel). Which way are they brighter?
3Explain
Step 1 of 5
A circuit is a complete loop
Electricity flows from the battery, through the wires and the bulb, and back to the battery. The loop must be complete for the bulb to light. The moving dots show the current.
4Practice
Question 1 of 5
Will the bulb light up?
5Recap
- A circuit needs a complete loop: battery → wire → bulb → wire → battery.
- A gap (like an open switch) stops the current.
- Conductors (metals) let electricity through; insulators (rubber, wood, plastic) block it.
- More batteries give more push, so bulbs are brighter.
- Bulbs in series share the push (dimmer); bulbs in parallel each get all of it (brighter).