Can 355 amps at 48 volts kill you?

>Given your body is a constant resistance,......

>>It isn't. You can get a good welding arc from 4 car batteries in series. You might want to touch that... I don't.

What is the relevance if that to our body's resistance?
 
It may mean little but having worked in labs for much of my working lifetime there were certain rules about what we were allowed to do and what was forbidden. On the electrical side we were not permitted to work on 230 volts AC or on DC over 50 volts. I assume there was good reason for this.
 
vyv_cox said:
It may mean little but having worked in labs for much of my working lifetime there were certain rules about what we were allowed to do and what was forbidden. On the electrical side we were not permitted to work on 230 volts AC or on DC over 50 volts. I assume there was good reason for this.
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The reason is normally that DC sends muscles into a continuous spasm, so whereas AC shocks tend to throw you away (that's one reason they have to strap people down to electric chairs), DC ones tend to make you grab the live whatever-it-is and prolong the shock indefinitely.
 
JumbleDuck said:
The reason is normally that DC sends muscles into a continuous spasm, so whereas AC shocks tend to throw you away (that's one reason they have to strap people down to electric chairs), DC ones tend to make you grab the live whatever-it-is and prolong the shock indefinitely.
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why dont they use DC for electric chairs.
 
JumbleDuck said:
I believe so, yes. Like the ohm (and the volt, and the amp) the siemens predates and was adopted by the SI system. From memory, the ohm and the siemens were originally competing units for resistance. It was decided in 1881 that the ohm would win, and by way of a consolation prise for the siemens supporters, the mho was dropped as the inverse ohm and the siemens used instead for conductance, admittance and susceptance. I bet that caused a confusing few years.

I'd love to know how the mho managed to survive, or perhaps to re-establish itself, in electronics. Certainly in the stuff I used to do in superconductivity and electromagnetic modelling everybody always used the siemens.
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LadyInBed said:
When I was first taught electronics in the late (19)60's it was the mho but when I did an upgrade course in the early 70's si units had kicked in.
Here's a thought, if you have more than one mho are they smho?
Sorry folks.
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FWIW, I learnt what little electrical knowledge I have as part of A-level Physics in the late 60s (exams in 1969 and 1970, I think!) I knew about the mho, but not about the siemens. However, we were still using CGS units rather than SI (Northern Universities Joint Matriculation Board). SI units didn't really start to make any impact on me until the 80s.
 
AntarcticPilot said:
FWIW, I learnt what little electrical knowledge I have as part of A-level Physics in the late 60s (exams in 1969 and 1970, I think!) I knew about the mho, but not about the siemens. However, we were still using CGS units rather than SI (Northern Universities Joint Matriculation Board). SI units didn't really start to make any impact on me until the 80s.
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Electromagnetic units in the cgs system were an utter nightmare, not least because there were several different systems of them. SI is much, much, much simpler. Nevertheless, I am pretty sure that all the cgs systems used the ohm and the siemens, so your physics syllabus had probably been written by electronics people. I am pretty sure that Scottish Higher Physics, a bit later than your A-level, used mhos as well.
 
JumbleDuck said:
The reason is normally that DC sends muscles into a continuous spasm, so whereas AC shocks tend to throw you away (that's one reason they have to strap people down to electric chairs), DC ones tend to make you grab the live whatever-it-is and prolong the shock indefinitely.
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My father was an electrical engineer in the coal pits in Ayrshire where DC was used underground, he always said DC held you and AC threw you. He credited my uncle, who worked with him, for saving his life when he was gripped by fairly major DC voltage and my uncle managed to cut the supply very rapidly.
 
I do think JumbleDuck may be confusing CGS with SI.

Around 1963 (in the Grammar! school) we were certainly being educated in CGS in science and maths. That was of course after having spent many years exercising ourselves on rods/poles/chains and furlongs (having mastered £SD and lbs-stones-cwt along the way).

I can clearly recall the physics and maths teachers getting quite excited about the 'new' SI units just before I went into 6th form around 1965.

Wikipedia (though by no means infallible) seems to agree.
 
jimi said:
My father was an electrical engineer in the coal pits in Ayrshire where DC was used underground, he always said DC held you and AC threw you. He credited my uncle, who worked with him, for saving his life when he was gripped by fairly major DC voltage and my uncle managed to cut the supply very rapidly.
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I have a book of electrical experiments for boys, published in the 1930s when there was a still a fair bit of DC mains around. One of the experimnts suggests that you find out what sort of mains you had by stripping the end of a bit of flex, plugging the other end in and dipping the bare wires into a glass of saltwater. Equal bubbles at both wires: AC mains. Twice as many at one: DC (and the double bubbles are the hydrogen and so the negative side).

They didn't have quite the same attitude to safety in those days. The same books suggests that, if you have AC mains, you connect up a big electromagnet under a table and amaze your family and friends by frying an egg in an metal flying pan on the table top. The induction hob, seventy years before they became common!
 
VicMallows said:
I do think JumbleDuck may be confusing CGS with SI.
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In what way? Electromagnetically speaking, cgs and SI are very different indeed. For example, cgs the permittivity of free space is 1 (dimensionless, so electric flux and electric field are dimensionally the same) whereas in SI it is 8.85 x 10-12 F/m. Similarly in cgs both B and H are magnetic fields with the same units whereas in SI B is magnetic flux (in teslas) and H is magnetic field (in A/m) and they are related by the permeability which is a dimensionless number in cgs and exactly 4 pi x 10-7 T m / A in SI.

The net effect of all of all this is that Maxwell's Equations, which describe everything in electromagnetism, look very different in the two systems and to those like myself brought up in the SI system, texts and papers in cgs - which I have had to read - are a right royal pain the bottom to translate.

Digression aside, units of measurement for electricity have never really changed: imperial, cgs, mks and SI have all used the amp, the volt, the ohm and, officially, the siemens.

Sorry about the length of this. It's a happy reminder of my research days - I spent many years doing numerical modelling of electromagnetic systems.
 
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