Consider a single phase system with 2 wires coming from the transformer, one hot and other neutral. These 2 wires are connected to my main box. The hot wire is connected to the breakers, then leading to a live pin of sockets. The neutral wire is connected to the neutral bar, and then connected to the neutral pin of sockets.

A green ground wire connects the ground pin of socket to the neutral bar. A wire connects the neutral bar to the literal ground in my garden. Why does not all electricity go into the ground?

  • $\begingroup$ To clarify: Are you asking why, when you connect a load to an electrical socket, does current not flow from hot, through the load, back to neutral bar, then to ground? Or are you considering when there is no load? $\endgroup$ – BMS Nov 18 '16 at 1:00
  • $\begingroup$ "Why does not all electricity go to the literal ground." - why do you think it would or should? $\endgroup$ – Alfred Centauri Nov 18 '16 at 1:18
  • $\begingroup$ @bms,yes,when there is load $\endgroup$ – Anon Nov 18 '16 at 1:32
  • $\begingroup$ @Alfred . Shortest path to ground is that green ground wire,given an option,electricity will pick shorter path? $\endgroup$ – Anon Nov 18 '16 at 1:33

The answer to this is that electricity does not always take "the shortest path to ground." That phrase is an oversimplification that can be useful, but in this case is not.

A more correct statement is that electricity flows from a high potential to a low potential. In the case of the power to you house, that means it travels in a loop between the power company and your house. That loop happens to have a single point where it connects to the "ground" under your feet, but that doesn't make a loop.

Well, it kinda does. The power plant is on the ground too, so in theory there are two parallel connections. One goes through one wire into your house, exits, and returns on the other wire, and the other goes through one wire into your house, exist, and then heads out to the "ground" and travels to the power plant along that path.

In reality, both paths are followed, all the time. However, the resistance of the ground between you and the power company is far larger than that of the wire, so the vast majority of the current travels through the wires.

  • $\begingroup$ So then,how does a ground protect me from being electrocuted?. In other words,how Is it that only excess electricity is transferred to ground,through the wire running into my garden. $\endgroup$ – Anon Nov 18 '16 at 2:14
  • $\begingroup$ The way we set up grounds is done such that the path for current to take through you has a far higher resistance than a path through the wires. To go much further than that, I'd need to ask what does "a ground" mean to you. 99% of the cases where grounds protect you have little to nothing to do with the fact that there is a path to the physical earth, and more to do with making sure the path of least resistance for the electricity is through the wires, not you. $\endgroup$ – Cort Ammon Nov 18 '16 at 2:18
  • $\begingroup$ Then what is the purpose of a path to physical earth through my garden? $\endgroup$ – Anon Nov 18 '16 at 2:37
  • $\begingroup$ It's for the 1% case. In theory, if one of your power lines got connected to the ground on a rainy day, it could cause a potential between the ground and the metal case of any grounded device. If you touched the ground and the metal case, the resistance of that path could be low enough to let a bunch of current flow through you and electrocute you. $\endgroup$ – Cort Ammon Nov 18 '16 at 2:40
  • $\begingroup$ By having a ground line, if the "hot" side of your powerlines ("hot" defined as the one not grounded) were to touch the ground on a rainy day, it'd form a loop through the ground and into the ground-wire. If that path had a low enough resistance, it would pop the breaker, preventing an electrocution. $\endgroup$ – Cort Ammon Nov 18 '16 at 2:42

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