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Electricity at Home: from the Power Plant to Your Socket · EPISODE 3 · 2:36

The Guards — Fuse, Circuit Breaker and RCD

Your kettle has a hidden fault. Touch it, and a small current flows through you — and your circuit breaker won't even notice. So what WILL save you? The fuse, the circuit breaker (overload vs short circuit) and the RCD / GFCI that catches the leak that kills, explained simply. Episode 3 of Electricity at Home, in under 3 minutes.

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What you'll learn

  • A fuse is a thin wire made to be the weakest spot. Too much current → it melts and breaks the loop before your wiring can overheat. It works once: replace it with the same rating, never a bigger fuse or a piece of wire.
  • A circuit breaker (MCB) does the same job and can be switched back on. Overload (too many heaters on one circuit): a bimetal strip warms, bends and trips it after a while. Short circuit (live touches neutral): a coil yanks the contacts open in milliseconds.
  • Each circuit's breaker matches its wires: lighting ≈ 6–10 A, sockets ≈ 15–20 A (UK ring circuits 32 A).
  • About 0.1 A (100 mA) through your body can stop your heart — 160 times less than a 16 A breaker even notices.
  • An RCD / RCCB (GFCI in the USA) compares the current out on live with the current back on neutral. If ≥ 30 mA (≈ 5 mA for a GFCI) is missing — leaking through you to the ground — it trips in a split second (typically ≈ 0.03 s, faster than a blink).
  • Press the TEST button about once a month. If it doesn't trip, call an electrician.
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Quick refreshers

EP.25 · Home Electrical · 1Find a hidden current leak with a clamp meter EP.40 · Home Electrical · 3RCCB: the switch that trips on a leak EP.41 · Home Electrical · 4MCB: overload vs short circuit HALF TRUE EP.96 · Myth or FactMyth or Fact: "It's the voltage that kills, not the current" MYTH EP.104 · Myth or FactMyth or Fact #7: "Rubber slippers make you 100 % safe from shock" EP.116 · Smart BuyerSmart Buyer #5: Power strip — what can it really handle?