Simple Circuit Builder
Build simple circuits: a complete loop is needed for current to flow; more cells push more current (Ohm’s law, V = I × R); series bulbs share the voltage while parallel bulbs each get the full voltage.
Before you try
What if you added a fourth bulb in a row? Would they all go dimmer or just the last one?
Try it out
Interactive activity
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What happened?
Move a control to see what changes and why.
The wires are perfect, with no resistance, and the battery never runs down. Real wires warm up slightly and real batteries fade.
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Try these ideas
- Add bulbs in series one at a time and watch the brightness.
- Switch to parallel with the same bulbs. What changes?
- Open the switch. Which bulbs go out?
Why it works
Electricity needs a complete loop (a closed circuit) to flow from the battery, through the bulbs and back. Open the switch and the loop breaks, so every bulb goes dark at once.
Bulbs in series sit one after another, so the battery’s push (voltage) is shared and each bulb glows dimmer. Bulbs in parallel each have their own loop to the battery, so each glows at full brightness, but the battery drains faster. The simulator uses Ohm’s law to compute current and brightness.
Check your understanding
Question 1 of 3
A bulb is connected to a battery but the switch is open. What happens?
Three identical bulbs are connected in series to one battery. Compared with one bulb, each glows…
A 3 V battery is connected to a 6 Ω bulb. What current flows?
Explain it in your own words
What changed? Why did it happen? Where might you notice this in everyday life?
For parents & teachers
- Find switches at home. What loop does each one open and close?
- Ask: why are house lights wired in parallel, not series?
- What happens to fairy lights wired in series when one bulb breaks?