Beginner lesson
Meet the circuit
Why does a light turn on? Follow the path and find out.
Free activities
Lessons and activities to try at home or in class. All free.
Explore the lesson
Try it on paper
Think like a switch
One small gap can change everything. Explore open and closed circuits.
Builder’s notebook
A little troubleshooting
When it doesn’t work yet, your next question is your best tool.
Try a paper circuit: series or parallel
Flip the paper switches. Try series, then parallel. Watch where the current goes.
Try a paper circuit at homeCircuit
Batteries
Paper switches
Parallel · 3 V · D1 on · D2 off —
S1 closes the first branch. D2’s branch is still open.
Why? In parallel, each LED gets the full 3 V across its own branch, more than the ~2 V a red LED needs.
Challenge: can you light both LEDs in series?