You have a sharp eye, Solarwind :) You caught the inconsistency in my explanation. In the example I gave, one could say that grip pressure and sweat change the resistance, but that the current to voltage relationship would still be linear. That might be true, I don't know enough about human skin. However, there ARE examples of materials and devices which do NOT follow Ohm's law. Diodes, for example. Their voltage drop is approximately the natural log of the current. Another example is a salt water solution with conductive electrodes stuck into it. I don't know what the voltage to current relation is here but I suspect that it is very nonlinear and, therefore, non-Ohmic. A spark gap is another. When a spark gap is NOT arcing, you can increase the voltage until it reaches the breakdown voltage (depends on the gap/electrode geometry, the gas they are in, presence of ionizing radiation, etc.). Up til this point, the current will be zero. Then, suddenly, the arc starts and the current begins to rise. As the current rises, the voltage actually DROPS. If you attach a current source to the arc, and you turn up the current, you will see the voltage go DOWN, instead of up as you would expect with an Ohmic material. I would suspect that skin has an Ohmic region (i.e., up to a certain voltage it will be mostly Ohmic), but that it behaves in a non-Ohmic fashion at higher voltages. Sean On Sun, Jul 5, 2009 at 9:41 PM, solarwind wrote: >> Ohm's law works very well for most metals. It is not a very good model >> for the human body. Sweat and grip pressure greatly change the amount >> of current which will flow for a given voltage. I also greatly suspect >> that, as the voltage climbs, there is a nonlinear increase in the >> amount of current due to electrochemical breakdown of the skin. Also, >> all bets are off once the skin is punctured because the internal body >> fluids are MUCH more conductive. >> >> Sean > > But it would still technically follow ohm's law since the resistance > of your body would change? > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist