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shows a transformer drum with a ground wire attached to the pole. Does this ground wire carry current (it must do as the other two wires are hot wires) or does a neutral run back from the house to the transformer meaning that the bare wire attached to the pole is just for safety.
Thank you.
Answer It is not a "drum" - it is a transformer mounted in its housing. (And, yes, I know howstuffworks used the term drum, but it is not common use in the electrical world.)
Ostensibly, no, the ground wire does NOT carry current at least is not a main current carrier for the delivery system but a protection and fall back in case there is trouble on the line. Let me explain.
The power delivery system to the transformer is actually a three phase system. It is delivered via 3 wires. The output of the transformer can be also 3 phase with a 120v difference between the phases. Hence the 120v to the house is actually from one phase to the other. The electric range, for example, and a heavy duty air conditioner may require 240v, so they are fed off the full phase of the 3 phase system. The electric company balances the wiring of the houses and the neighborhood such that the load is the same on all three phases and the system is in balance. If it goes out of balance due to load conditions or a fault on one of the legs, then there is heavy current through the ground line. However, there are sensing circuits that immediately try to correct and if not, a work crew is sent out to find the fault conditions on the line.
Therefore, the ground line is for safety and for leakage, but it is not the main return carrier of the power.
Lastly, electricity does not flow by electrons. Actual electron migration along the wire is very slow. What actually happens is a charge "hole" or a place where an electron just left is what travels. And it travels approximately at the speed of light.
An exception to this conduction principle is in a vacuum tube where electrons are actually boiled off a cathode and they do travel through the gaseous space to a collector or plate that then continues as above.
In electrical engineering courses at the university level current always flows from the plus terminal to the minus terminal because this is the way it actually goes in the physical world. High school and lower level text books use the negative flow of current, from the negative terminal to the positive terminal, because it is easier to conceptulize - but it is wrong!
