Dangerous Capacitor

ericgibbs said:

Your statement about DC not causing a person to stick [muscle contraction] is incorrect.

I would suggest that you do some more research into electrocution causes.

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I have done and all sources I can find, that give actual figures, all list higher let go currents for DC than AC.

PAT Information - Electric Shock, Dangers, Effects, First Aid

. For DC, the let-go current is about 75 mA for a 70-kg man. For alternating current, the let go current is about 15 mA, dependent on muscle mass.

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**broken link removed**

DC tends to cause the muscles to contract and this often makes one pull away from the source. AC often causes muscle tetany and "freezes" the hand to the source, thereby increasing the time exposed to the electricity. The "let-go" current is the highest amperage at which you will still be able to pull your hand away when you receive a shock.



For DC this is about 75 milliamperes (mA) and for AC it's about 15 mA depending on the person's muscle mass (the higher the muscle mass, the higher the cut-off amperage).

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Handbook of psychophysiology - Google Book Search


This book says at currents over 99mA for DC and 22mA for 99% of people can't let go.



Unfortunately Google books doesn't support copy and past (for obvious reasons).


I've had this argument before with a lecturer but I was arguing that AC was safer. He told me to go to the library and find a few books that said AC was safer. After doing lots of research I realised I was wrong - even more so when I received DC vs AC shocks when experimenting.

hi hero,

I'll look thru your links, thanks.

My concern is the Newbies who read our posts may misunderstand our discussions and come to the wrong conclusion that is to say, 50V to 110V is safe and no precautions need to be taken.

I would rather err on the side of safety and say to Newbies that under certain conditions, 50V to 110V [and over] can be lethal and when working on voltages over 48V precautions must be taken to avoid electric shock hazards.

Regards

Agreed.

I think one of the worst myths is that the skin effect protects you from high frequency 100kHz AC (Wikipedia even says this). The truth is, it doesn't. Human flesh is too poorer conductor for the skin effect to be very pronounced. If the skin effect provided sufficient protection then microwave ovens wouldn't deeply heat meat because the skin effect would stop them from penetrating to the core and we all know this isn't true.

The truth is that the nervous system doesn't respond to high frequencies so the deadly asphyxiation and ventricular fibrillation don't occur, you still get cooked though. RF burns can be deep and are often worse since they damage tissue where there is no pain receptors so you don't even know you're cooking.

Additional electric chair question:

Hello,
in terms of Joules as a unit of measurement, what is the typical load that a traditional electric chair would deliver, let's say that 200,000 V is delivered at 8 amps over approximately 15 seconds??
Thanks for any available math help
chris

Chair continued...

So then, in other words, would it be acceptable to say a statement like, "so & so got "x" amount of joules delivered via the chair at his execution - or is there a more widely accepted term to use? In other words, if referring to the condemned, "what " is it that he is receiving - joules, amps, volts - all 3 or none of these? And I am assing the the Ohms, or resistance, are not bring received by the victim, but instead are an inherent form of bodily/tactile resistance to the load?? Please clarify, and thanks so much. I'm actually an xray tech lol!