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Cake day: March 8th, 2025

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  • Nope. Circuit breakers do not break on absolute current values.

    Huh, TIL.

    Ever. Period. At all.

    That doesn’t seem to be supported by my research. Standard breakers are designed to trip based on a function of over-current and time, but that doesn’t preclude any breakers from using current alone.

    Even a basic spec sheet will inform you as much…

    It won’t. I checked. A more detailed spec sheet will, but not a basic one.

    It’s why many euro firms make fun of American standards: They’re literally not expressive of reality.

    They sure look like they are. The rating is the current that the breaker can sustain indefinitely at the reference temperature. And it sure looks like the EU rates them the same way.

    Even GFCI’s can shock the fuck out of you in certain circumstances.

    Of course they can. You aren’t a ground fault. A load of 100mA on a GFCI is perfectly normal, and the same load will kill a human very quickly.


  • kkj@lemmy.dbzer0.comtoNo Stupid Questions@lemmy.world[Electrical hazards] Electricity is complicated... ⚡
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    Aquileo | edit-2
    10 hours ago

    It’s 100% current, but the current that matters is the current through you. The resistance between your hands is roughly 3 kΩ at low voltages and about 1 kΩ at 220V. You need about 5 mA DC or 1 mA AC to feel anything, which means you need about 15V DC if you’re the only resistance in the circuit.

    The current at your outlet will be ~0.05A if the only path between hot and neutral is the transformer. If you add an alternate path, you allow for up to 25A or so before the breaker cuts the circuit. 25A would mean that the resistance between hot and neutral is about 8Ω. If you are the alternate path, there will be about 220V/1k=220mA going through you, which is about 8x the amount needed to cause you to go into cardiac arrest.

    The only time that the current in the outlet while the transformer is connected would matter is if you were in series with the transformer. If you stuck a wire into each side of the outlet and connected one to one side of the transformer, then grabbed the other wire with one hand and the other side of the transformer with the other hand, you’d experience a shock of about 55 mA (0.05 A, like you calculated), which would still probably kill you.

    The button cell doesn’t do anything because it’s 1.2V. That means its max current through your body is about 0.4 mA, or 0.0004A. It’s also DC, which means that it affects your body about 5x less than the AC in your wall outlet.