A switch is a gap you can close
Taking a wire off every time is slow. A paper clip on a pin works better.
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The idea
Step 1 of 3
- The switch is open. There is a gap. The lamp is dark.
- The switch is closed. The gap is gone. The lamp lights.
- The cell is taken out. The switch is closed, but the lamp stays dark.
The rule
A switch opens or closes the gap. ON is closed. OFF is open.
When a switch is OFF, its two ends do not touch. Air lies between them. So no current crosses the gap.
A closed switch alone does not light the lamp. The loop also needs a cell.
With two switches on one loop, both must be closed. If either switch is open, the lamp goes dark.