I How realistic is the term "ground"

[CraigHB]

The Earth is a conductor. All conductors have capacitance as well as resistance and inductance as small or large as those values may be. It is possible to claim a capacitance for the Earth but it also has to be between two specified points. Trying to assign a value to the Earth in general may be meaningless since if it were possible to stick a probe at either end of the Earth and measure, values would vary depending on the location of those two points.

The term ground comes from a time in early physics when Earth ground and electrical ground where the same thing. The term is still used as the zero reference for electric potential, but ground for a circuit and ground for the Earth may or may not be at the same potential. In circuit analysis you can assign zero potential to any node calling it ground and calculations are still valid.

For example utility electrical systems use a ground that is in fact Earth ground. However a device not in contact with Earth ground may have a ground with higher or lower potential. The problem is sometimes ground is in fact Earth ground and sometimes it's only a common node in a circuit used as a zero reference. It's a term that does a poor job of clarifying itself.

 

[Beanyboy]

The "Volts" are an electric potential. You can raise your body's electric potential to many Volts (don't try it) and not be harmed as long as you make sure that your entire body is an equipotential and you are far from objects across which a spark can jump at you. Again, don't try this. What is harmful, is a potential difference or voltage between two points in your body because then a current (amps) flows between these two points according to Ohm's law and, if your heart happens to be in the way, its electrical signals get messed up and goes into atrial fibrillation which could be lethal. It's a hard way to learn the difference between electric potential and voltage.

I'm rather partial to the auld heart all the same, so I think I'll pass on sending any unnecessary volts through this crumbling body of mine.