Staircase lighting circuit – schematic and installation diagrams
Design & TechnologyElectrical Engineering & SafetyAges 14–15
Use it with your class: students open it from a link or a QR code, with no account needed.
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A staircase lighting circuit uses two two-way switches to control one lamp from two locations, with an optional intermediate switch added to control it from three locations. Students click each switch to toggle it, watch which wire is carrying current and whether the lamp is on or off, and switch between the schematic diagram (showing the switch terminals) and the installation diagram (distribution board, conduit, and ceiling lamp). The Check continuity button highlights the wire that is currently live and calculates the current I = P/U.
Lesson: Installing a two-way switching circuit for one lamp using two two-way switches: schematic diagram, installation diagram, wiring, and testing
What it shows
A two-way switching circuit lets one lamp be controlled from two places, such as the bottom and top of a staircase. Each two-way switch has a common terminal that connects to one of two other terminals, and two traveler wires link the switches. The lamp lights only when both commons connect to the same traveler, so flipping either switch always changes the lamp's state. An intermediate switch crosses the travelers over and adds a third control point. The switches interrupt the live wire, and the lamps are in parallel, so the supply current is the total power divided by the voltage.
How to use
Start with Two two-way switches – one lamp (staircase circuit) and click each switch in the diagram, filling in the state table for all four combinations. Turn on Show current flow direction in the wires to trace which traveler carries the current. Press View installation diagram to see where the same wires run in the house, then Check continuity to test the circuit and read I = P/U. Finally change to the three-location circuit and repeat.
Parameters you can change
- Circuit to install One single switch – one lamp, Two two-way switches – one lamp (staircase circuit), Two two-way switches + one intermediate switch – three locations
- Diagram type shown Schematic diagram, Installation diagram
- Power of each lamp 5–100 W
- Number of lamps in parallel 1–3 lamps
- Show current flow direction in the wires
Questions to explore
- Which switch combinations light the lamp in the staircase circuit, and what do they have in common?
- What does the intermediate switch do to the two traveler wires, and why does that add a third control point?
- How does the current change when three lamps are connected in parallel instead of one?
