Which would be more dangerous for a human being 230 V a.c or 230 V dc supply...
Assuming enough current both can kill you.
People say that the DC is more lethal and painful because it runs through the center, while the AC is concentrated around of the conductor.
does anyone know if it's true?
Not really, at higher frequencies AC travels in the surface of a conductor (the skin effect) but that's not relevant here.
AC can kill you at very low currents (0.01A) because the heart uses electrical signals. A small 50/60Hz AC current through the heart causes it to try and beat at 50/60 times per second which doesn't work for very long.
DC kills you be simply burning so you need a lot more current.
But high power DC can be a lot more dangerous in use. It's very difficult to switch off DC or disconnect something that is attached to it.
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