This is something that has bothered me since high school physics. I have a medical and engineering degree, yet I can't for my life answer this question in a way that's logically consistent in my head. The question essentially boils down to the following:
A high voltage line is about 20,000V. This is considered a "high voltage" injury if you touch this line and get shocked. Yet, the voltage between you and a door knob when you get shocked is also about 20,000V. The reason you don't die from the doorknob, is because the current from the doorknob is microscopic compared to that of the power line. But if $V=iR$, and the $V$ is fixed, and the $R$ (my body) is also fixed, what's allowing the higher current?
I know there's something wrong with my oversimplification of the situation that prevents me from fully understanding this but I can't seem to get my brain around it.
Now of course the damage you receive is actually determined by the total energy transmitted which is $W = Pt = iVt = i^2Rt$, so time plays an obvious role in the damage received from electrical injury. However, I still can't wrap my brain around the idea that you can generate more current with the same voltage.
An analogy I guess is putting batteries in parallel, which increases their current handling. Yet if you hook up a single 1.5V battery to my body, and 6 1.5V batteries in parallel to my body, the current - by Ohm's law - should stay the same, no? What am I missing here?
So can someone finally explain to me how the powerline kills me but the doorknob just gives me a tickle?