Ground? Where?

[gravityblock]

Equalizing potential differences and grounding are two different things.  The Helicopter you mention does this for safety...

I once knew someone that tested the lines like this, he mentioned a colleague that was injured because the path didn't go to the probe but decided to ground out to one of his dental fillings instead.  This doesn't stop the discharge from being unpredictable.  It seems to do what it wants.

If the car were grounded, I think the battery would leak.

The probe allows them to equalize the voltage potential.  The metal fibers in their suits is acting as the ground which allows them to work as safely as possible in this type of environment, since the energy will flow around them instead of through them.  The earth ground accomplishes the same thing, it diverts the unwanted energy away just like the metal fibers in their suits.  Grounding is about diverting the unwanted energy to a safer place in order to avoid damage, etc to sensitive equipment and life.  Both the shielding and the earth ground diverts the unwanted energy to a safer path.  They have the same purpose and accomplishing the same thing.  Both are "grounding methods".  The only difference is the terminology used across different fields, which is just a play on words.  Now, shielding can be used for other purposes also.

A car battery does have one terminal connected to the metal frame and it doesn't leak because it is an open circuit.  This connection between the battery and frame is called the "ground cable".  In order for it to leak, then both terminals would need to be connected to the frame and that would create a short and discharge the battery in a bad way.  Same thing if it was connected to an earth ground. 

Here's a link showing the battery is connected to the frame on a car.  On the link page scroll down to "Operating Instructions" and you can see they call this the "negative ground" if the negative terminal is connected to the frame, http://www.battery-chargers.com/charging_instructions.htm .  Do you see a pattern here?  The pattern is the negative ground, positive ground, neutral ground, and earth ground.  They're all describing the "grounding method"!

If you're holding the earth ground, and unwanted energy flows through it for whatever reason, then you're toast just like the guy having dental fillings.  In any grounding method, the unwanted energy can always jump to where it's not wanted, especially if you're near or part of it's path.  This is the whole purpose of diverting this unwanted energy to a "safer place" with any grounding method.  The further away you are from the path of this diverted unwanted energy, the safer you are!

Let's not over-complicate this.  Grounding is a really simple concept with many different methods using the same basic principals.

[IotaYodi]

the BX, with no real ground wire, was run to a lamp over the sink.  They switched the Neutral just to allow a plug for a clock to run off the same wire, drawing power from hot to the BX case.  That one scared me when I saw it.

Wow! If an electrician did it he needs to find a different job. Ive seen Mexican migrant workers run an extension cord through a window for the water pump. I watched some seemingly experienced Mexican electricians twist joints to the left and then put a wire cap on. An inspector would never see that.

[angryScientist]

Think Auto's, and Positive Ground.  The word "Ground" technically means the "Reference" 0 Volts assumed.  We chose what that is.

It has been proven, by the way, that the "Earth"  (Commonly thought of as "Ground"...) has a reference potential relative to space normal, but that actually has no effect on our use of the "Reference" meaning, so most will accept the earth, in an unexcited state, to be "Ground".

So the shell of the car is at a lower electron density than the wiring. What happens to the electron flow between the vehicle and earth-ground, or the atmosphere?

[jadaro2600]

Thank you all for posting the information, It answers a lot of questions about grounding.

Wellheads are notorious strikes ...

Also, I remember a tree that got struck in the neighborhood, it blew all of the bark off the tree and scattered it across acres.  I've never quite heard an explosion like that, It woke me from a dead sleep.

Perhaps the depth of the grounding rod has something to do with it's tendency to act like a lightning rod.  My air conditioner got struck once, I think it has a puny grounding rod next to it...   It still fried the heat pump though.

[nitinnun]

on a space ship, they would have a sandbox.
with sand, calcium, and carbon in it.
though having some water in the sandbox, would also help.


the paramagnetism of the sand and calcium, would generate the negative magnetism.
the electrical conductivity of the carbon, would unify the sand and calcium.



if a crew member stuck a wire into the sandbox, than the wire would be grounded.
the larger the sand box, the better the grounding.