How do an MCB and a switchboard work?

A strip of two metals, a tiny electromagnet and a stack of steel plates stand between your wiring and a fire. Power comes from the pole through the electricity company's cut-out and your meter into the distribution board. Inside an MCB the current runs through a coil and a bimetal strip.

Read how it works: How do an MCB and a switchboard work? · The history of the circuit breaker · More boxes on Glassbox

Chapters in this interactive model

1. The distribution board in your home: From the meter to a row of switches: where every circuit in the house begins.
2. Inside an MCB: two ways to trip: A slow bending strip for overloads, a fast electromagnet for short circuits, and a chute that kills the spark.
3. Trip curves: how fast is fast enough?: Pick a rating and a curve, set a current, and read off how long the MCB waits.
4. Faults: which device saves the day?: Overload, short circuit, earth fault, loose neutral, water. Ohm’s law tells you the current, and the current tells you who trips.
5. The RCCB: counting what doesn’t come back: A ring of iron compares the current going out with the current coming back, and trips on a difference of 30 mA.
6. Switches, sockets and wires, safely: Why the switch goes in the phase, why sockets come in two sizes, and how thick a wire has to be.