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Why did the breaker trip? (piefed.cdn.blahaj.zone)
submitted 4 days ago by to c/techsupport@lemmy.world
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I was relaxing in my sofa when I heard a pop. Then a clack. Then a beep.

I had forgotten to turn off the stove when removing a pot from it and my rice cooker's power cable dropped onto it. I suppose the first pop was the cable igniting. The clack was the breaker tripping and the beep was my UPS turning on. Nobody was hurt.

Resistance increases with heat. My power outlets supply 220~240 volts. Since I = V / R, the increased heat and resistance in the rice cooker's power cable should have decreased the current, if the outlet voltage is constant. Or, is it so that the system actually tries to compensate with more voltage within some range set by my electricity supplier? Or, was it something else entirely that tripped the breaker?

Please teach me! ๐Ÿ˜Š

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[โ€“] 2 points 4 days ago* (last edited 4 days ago)

Here's a DC Ohm's Law example from my work.

'80s Atari arcade games have a voltage sensing circuit that connects back to the power supply. The game has a mostly constant current draw; all the semiconductors are connected to the PSU so they can do their jobs.

As the game ages and connector pins oxidize, resistance goes up. Resistance going up means the power supply slowly adjusts its own voltage up to keep the current constant. Higher voltage in the wires means more waste heat, which increases the rate of oxidation... It's fairly common to see burned "card edge" connectors and melted plastic, but the game still works... until the chips start having their own failures from the higher voltage and heat.

Once, I put one of the Atari custom chips with blackened legs in tarnish remover and half of the legs completely dissolved. Soldered new legs on and refurbish the card edge connectors - all good!

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