In alt.home.repair, on Fri, 3 Mar 2017 08:37:23 -0800 (PST), TimR
wrote:

On Friday, March 3, 2017 at 11:27:20 AM UTC-5, wrote:
On Fri, 3 Mar 2017 05:16:03 -0800 (PST), John G
wrote:

The current on that ground will be on every ground wire in your house.

I think you mean voltage.

Not exactly true. It will just be on the grounding conductor going
back to the main bonding jumper, that one circuit. (unless you have

Going down to where the ground wire is broken (if it ever gets broken.)

If it's broken, it will iiuc have 110 volts, but the moment the current
begins to flow, the resistance of the timer/wall switch will lower it
tremendously.

You could do this test yourself. Take a lamp, cut the cord down the
middle and then cut the neutral wire, the wire that would have gotten
plugged into the wide slot (whether the plug is polarized or not, one
can tell which wire goes to the narrow slot and which would have gone
the wide one, by looking or with a meter.) Plug the lamp in, then
measure the voltage at the cut end of the wire from the lamp. it will
be 110VAC or so but if you touch it, even if another** part of you is
grounded , you'll only get the electricity that can squeeze through the
lightbulb. **But don't let it flow through your heart, your torso.
Don't hold the wire in one hand and use your other hand to ground
yourself. Even if it is teeny and probably can't hurt you.

If it's not broken, even the voltage on the ground wire in question will
be next to zero, because the wire is grounded. If there is some
resistance in the wire between where you touch it and the fuse box, and
of course there's maybe 0.00001 ohms or even 0.001 then the voltage
present will be found with E=IR, say 0.001 x 0.005 amps which = 0.00005
volts.

And that is just that one ground wire and everything connected to it,
not all the other ground wires in the house, which have to pass by the
grounded busbar to get to the wire in question.

bonded that EGC to other circuits down stream of the MBJ)
In normal installation these are star wired.
It still can present a hazard and it is still a 250.6 violation.

I agree it's a violation but the hazard part would require a couple of other faults, wouldn't it?

If a ground carries current but is at ground potential, seems like you shouldn't get a shock. If the ground conductor was broken anywhere on the path back to the main panel, all the connected grounds would be hot. But then your light wouldn't work, you'd know you had a missing ground.

Right, all the connected grounds, but this is a light-circuit only, so
that's the hall, front door light I think, dining room, kitchen, and
range hood lights, and the grounds in the switch boxes. It won't
include the ground pin on receptacles.