Household electrical circuit – fuse, switch, socket and overload
Design & TechnologyElectrical Engineering & SafetyAges 13–14
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Electrical Engineering & Safety
A diagram of a 220 V household circuit: supply → protective device (fuse or circuit breaker) → parallel branches of switch–lamp pairs and a socket. Students click switches to turn lamps on, plug a device into the socket, and watch the total power and current I = P/U; when the current exceeds the rated value, the fuse heats up and blows (or the breaker trips) and the whole circuit loses power. Replace the fuse or reset the breaker to continue.
Lesson: Overview of electrical circuits: power source, conductors, switching devices, protective devices and loads; electrical safety under overload
What it shows
A household circuit connects its loads in parallel, so every lamp and appliance receives the full supply voltage and can be switched on its own, while the branch currents add up in the supply wire. The total current follows from I = P/U. A protective device limits this current: a fuse contains a thin wire that melts when the current exceeds its rating, and a circuit breaker trips and can then be reset. The rating must suit the total load and the wiring, which is why a blown fuse must never be replaced with a higher-rated one: the wires would overheat before it blew.
How to use
Set Number of lamps and Power of each lamp, then click the switches to turn the lamps on one by one and watch the total power and current rise. Choose a Device plugged into socket, moving from the fan up to the kettle or hot plate, until the current exceeds the rating. Compare the two Protective device options, reduce the load, replace the fuse or reset the breaker, and then change the rated current and try again.
Parameters you can change
- Number of lamps 1–5 lamps
- Power of each lamp 15–200 W
- Device plugged into socket Nothing plugged in, Electric fan 60 W, TV 100 W, Iron 1000 W, Electric kettle 1800 W, Electric hot plate 2000 W
- Rated current of the fuse / breaker 2–20 A
- Protective device Fuse, Circuit breaker (CB)
Questions to explore
- How does the total current change each time another lamp is switched on, and why?
- Which combinations of lamps and appliances overload a 5 A fuse, and which are still safe?
- Why is it dangerous to replace a blown fuse with one of a much higher rating?
