Electricity Flow and Ground Wire Pre-face: My step-father and I were turning the heat down on the water heater. He demonstrated that touching the ground wire doesn't shock you.
My understanding is that the ground wire doesn't have current unless the case of a short-circuit, or over-abundance of energy. The wire also has very little resistance.
My question, if the water heater had a short-circuit or had an access flow of energy. Would he have been shocked? Please explain instead of yes or no.
 A: No.
The elementary idea of grounding is that excess current finds an easier way to the ground than through your body.
If you're wet, you 'may' in minimal probability get a minor shock, but unless your body offers the current a path easier or at least comparable to the metallic ground wire, the answer is no.
EDIT: Current gets divided in inverse ratio to resistance offered by the paths, hence very less or in this case negligible current flows through a path which has a very high resistance compared to the other.
A: The answer is "no".  Assume that the ground wire has a resistance of 1 ohm, and your step father has a resistance of 100,000 ohms, which is actually a bit lower than the "normal" value when measured with dry hands.  This means that your step father will experience a current flow that is 1/100,000 times the current flow through the ground wire, assuming that there is a short circuit in the water heater.  In addition, since the ground wire has such a low resistance, there will be a LARGE current flow through it.  This current flow will immediately trip the associated circuit breaker, shutting off current to the water heater.  Unless your step father happens to be touching the ground wire at EXACTLY the time that the short circuit happens, there will be no current flowing through him.  Even if he is unlucky enough to touch the ground wire at the exact wrong time, the current flow through him will be so low, and last for such a short duration, that no harm will occur.
