It does vary a lot depending on the person their skin and the contact area you are using. If the person is sweating at the time this makes a difference as well. I recall a project from my misspent youth of trying to make this resistance produce tones like chill out bio feedback music, (far out dude) However the variation in the connections and other weird effects actually produced some terribly annoying bleeps pulses and groans. The resistance is in the millions of ohms, so it should not have surprised me I suppose that only very slight variations due to contacts etc, would make a huge change to it.
I was using FET gates to do the detection as I recall, as they were inherently high impedance. You had to filter out the 50 hz though or the sound was rather like a Dalek with piles. Brian
Or is standing on a tin tray. Also one other issue that made me give up was static electricity, which could suddenly discharge and cause spikes in the sound. It was better if you were naked, but then its not always a good look....
Strictly speaking, he's right, though. IIRC, impedance is the resistive component plus the reactive component combined vectorally from the square root of the sum of the squares, thus:
z= sqrt(r^2+x^2)
And since we're talking AC, albeit only 50hz, z is still the correct parameter to consider.
Gee, no kidding, H? Seriously, approximations ARE made for such purposes as you presumably well know. The so-called 'human body model' springs to mind. Here's an interesting article that's germane to the discussion:
We used to get the apprentices with one by holding the leads tightly and getting them to wind it then reverse rolls, the trick is that if you hold the leads tightly the shock is not bad as long as you don't let go but they usually do and get the full benefit.
Not only that, it is common in shock risk scenarios to look at the earth loop impedance - i.e. the total round trip impedance taking into account all the various aspects that will affect total current flow in any given situation.
I see you use that as a kind of flag... I presume it highlights that whatever you are about to write is drivel? That certainly seems to be the case!
No, you need to learn a bit of very basic electrical theory...
Any capacitance will be in parallel with the DC resistance. With AC that capacitance will present a reactance inversely proportional to frequency. Therefore any non infinite reactance will lower the overall impedance. (go read up on impedances in parallel)
No, again internal capacitive effects will result in the cell membranes passing AC better than DC. This applies to the skin as well. Changing voltages are better able to penetrate than static ones.
AC will also make muscle tissue attempt to contract in sympathy with the frequency. Since they can't respond at 50/60 Hz this can result in tetanic contraction and loss of voluntary muscle control. This is what can prevent you being able to "let go" of live item and thus prolonging the shock duration.
The heart muscle is most vulnerable to changing electrical stimulus, and so is far more likely to be affected and driven into fibrillation by AC than with DC. (with DC shocks you have to start the shock during a fairly short temporal window in the regular rhythm to cause the same effect)
Lastly with DC shocks, you tend to feel the initial contact and the disconnection, whereas with AC you will feel pain for the duration.
340 actually, but close.
The voltage level, the magnitude of the current passed, rise time, and the frequency. Note also that nervous system effects are not the only deleterious effects of shock.
So as usual, pompous drivel The human body can act as one plate in a capacitor when wearing insulting materials and stood on a conductive surface. There is no capacitance within it. Nor can there be as electric charges are held one the surface of insulators. Can't think of any insulating material within the human body to form a capacitor.
My apprentices can mange to get their own electrical shocks.
Me "Do not touch that cable it might be live, I'll go and turn the power off"
So I went to the cellar and turned the power off at the two CUs I could find. On the way back out of the cellar the joiner said "Your apprentice has touched the cable and he got a right belt from it".
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