Volts, current and not becoming dead

11 January 2024

The article below (“Beware Low Amp Current”) caught my eye, and I thought it was worth reposting to the group. I don’t like the term “Low Amp Current” – ugh. But the situation described is very real: it’s current flow through the body that kills you, not the presence of high voltage.

Of course, anyone who knows Ohm’s law will point out that for a given resistance (your body) more volts means more current flow. So duh: you’re more likely to die if you contact a high voltage, but a 12V battery could do lots of damage if under some bizarre circumstances >50mA could flow through a body. Note that if the source of volts is high but can’t deliver enough current then you’re marginally safer. Think static electricity, which is very high voltage, miniscule current, and very short time interval. Nasty but much less dangerous than hanging on to 240V for a while.

But a static discharge of 500mJ is possible from a human body, and it only takes 2mJ to ignite hydrocarbon vapours.

Sidebar: your body chemistry is affected differently by different voltages. Even though both can kill, 240V is more severe on the body than 110V, and the impacts are different; that’s one of the reasons why our US friends have been able to get away with what we would flag as APPALLING safety processes in some very common media industry applications. Also: AC does nasty things to the body at lower voltages than DC.

Simple moral: It’s like driving or flying: don’t take risks, and don’t ever get complacent around power circuits of any sort.