k0ua
Epic Contributor
How do the electrons "know" which is the shortest path? do they measure it first? and is the shortest (distance )path the lowest resistance in all cases? answer, NO. Electrons flow in all conductive paths, the resistance of each conductive path determines the amount of current that will flow in that path. Ohms Law E=IR you can calculate the amount of current if the (E Electromotive force) is known and the (R Resistance) is know or can be measured. you will then know the (I current in Amperes)
Now before someone mentions Capacitive or Inductive Reactance in AC complex circuits or even skin effect in RF circuits, this is not what we are talking about here. We are talking about DC here to make this point. Lets say its a cool day and you are pretty dry, and you touch the positive terminal of a 12 volt battery on your tractor that is powering your lights. The lights are going to be drawing around 10 amps of current, a pretty sizable amount. Your skin even if it was pretty damp is going to limit the current to a very small amount at 12 volts. probably in the neighborhood a few milliamps or 10s of milliamps due to the pretty high resistance of your skin. Now do the exact same thing to a 48 volt electic fork truck this time you are going to feel it, as the current is 4 times more, and if you are really salty sweaty you are going to feel it even more as your resistance is less and the current will be much higher.. Remember the fork truck is still lighting those lights, but you got shocked, how can that be? "electricity always takes the path of least resistance or electricity always takes the shortest path right" bull-feathers electricity takes all paths. the path thru the copper wiring powering the lights with a very high current and the path thru your sweaty skin with much much less current. (but still enough for you to feel. Or how about this one..open your breaker box, take your shoes off have sweaty feet and stand on the damp concrete floor of your shop. Now have all the lights, air conditioning and everythig else in the shop on. maybe the load could be pulling lets say 50 to 100 amperes from the 240 volt mains. A lot of current going thru that low resistance copper wire, and your little body has a lot of resistance compared to copper wire even sopping wet. but let me tell you what will happen when you touch even 1 phase of that entrance circuit.. you are likely to be killed. or at least have the holy.... knocked out of you. But the current flowing in you will be very small compared to the current flowing in the copper wires, thru all the loads (appliances) back to the neutral. so why did not the electrons take the shortest (least resistance ) path ? well they did, but they also took the relatively high resistance path also (you). If you were very very dry, (this is a cold winters day in canada with the humidity around 10%) and you touched 1 of the phases. you may just get a tingle or little jolt.. because your resistance is very very high. but you still got some of the electrons. Because Electrons dont know anything, about paths, or what resistance those paths have. They flow in "All Paths" end of book.
James K0UA
