How does circuit complete through ground(earth)?

[K8MHZ]

If we allow electrocution survivors, next stop is non-lethal executions, immobile automobiles, inaudible telephones and invisible televisions. No sorry the slippery-pope fallacy doesn't apply.. – geotheory Dec 22 '14 at 13:30

 

[Besoeker]

The term electrocute was originally coined in 1889¹ by splicing the prefix electro- into the wordexecute. It originally meant execute (by electric shock). However, its meaning has evolved over time: first to also include accidental death by electric shock and later to include electrical injury,²generally serious in nature. So your use of the word does not fit the original nineteenth century meaning, but is perfectly in line with the broader meaning of the word as it is understood today.
https://english.stackexchange.com/q...-they-have-to-die-or-can-they-just-be-injured

Well, we both survived the shocking experience although he was a bit jumpy for a bit.

 

[K8MHZ]

Well, we both survived the shocking experience although he was a bit jumpy for a bit.

:lol::lol:

 

[GoldDigger]

...
... No sorry the slippery-pope fallacy doesn't apply.. – geotheory Dec 22 '14 at 13:30

Is that some kind of Catholic in joke?

 

[K8MHZ]

Is that some kind of Catholic in joke?

I didn't even notice that! My mind saw 'slippery slope'.

Good catch!

 

[kwired]

The way the DC on an electric fence designed for animal control is pulsed, there is time for the animal to jerk back or fall over, so they only get one pulse.
Electric fences designed for security may not pulse that way and would be a much greater hazard.

I once had a fencer around garden in an attempt to keep out rabbits, raccoons, etc. It was a unit intended for use for pets. I kept finding dead birds next to it, so apparently they couldn't take it.

I have been knocked unconscious by fencers designed for cattle before, happened to take a hit from it in the head and next thing I remember was picking myself up off the ground.

 

[MAC702]

...next thing I remember was picking myself up off the ground.

On Tuesday.

 

[roy167]

171001-1211 EDT

roy167:

You need to take a course on basic electrical theory. The first would be DC circuits, and the second AC circuits.

Some simple basics are:
1. The sum of the voltages around a closed loop is zero.
2. The sum of the currents at a point is zero.
3. v = i*r, and extended to AC v =i*z.

Consider a 12 V battery floating out in space with a resistive load, no connection to earth. Infinite resistance from either terminal to earth.

You have very dry hands, and using an ohmmeter you measure 1 megohm between your hands. For many dry hand people this is above 500,000 ohms. You grab the battery terminals with your two hands. The current flow is so low you won't feel a tingle.

Change your hands to very sweaty. Now the resistance between hands might be 10,000 ohms or less. Now you should feel a tingle from about 1 mA of current.

Continue with sweaty hands. With no connection to earth for the battery connect your sweaty hands between either terminal of the isolated battery and earth. Now we have an infinite resistance in series with 10,000 ohms for a closed loop load on the battery of infinity, and there is no tingle because no current flows.

Change the previous paragraph to have a wire from the negative terminal to earth. Connect one sweaty hand to the negative terminal and the other hand to earth. No voltage difference, no current, and no tingle. Change the first hand to the positive terminal and now with an assumption that earth resistance is 100 ohms from the battery earth connection point and your hand to earth connection. Loop resistance is about 10,100 ohms. You still have about 1 mA of current, and a tingle.

My soil has a remote earth to ground rod resistance of about 15 ohms. Two such points only add to 30 ohms, thus, less than the assumed 100 ohms above.

.

Hi, I know the theory. My question still remains

Can earth act as a return path on its own?

Can the current flow merely because there is a potential difference? or for current to flow, there need to be return path to the source? Along with potential difference.

It seems earth does act as a conductor although may not be effective return path as in bonding. The current should not flow simply because of the potential difference unless there is a return path. So, in the above example, if the transformer secondary is UNgrounded and person touches the HOT wire, there should be no current flowing through his body.

 

[winnie]

Hi, I know the theory. My question still remains

Can earth act as a return path on its own?

No, you must have a closed circuit.

Now, the Earth is very large, and can act as a 'plate' of a capacitor, and AC current can flow through a capacitor, so even if you have a completely galvanically isolated transformer you can have a tiny bit of current flow, but with reasonable transformers this is pretty negligible.

Can the current flow merely because there is a potential difference? or for current to flow, there need to be return path to the source? Along with potential difference.

If there is a potential difference, then current will flow. But if you do not have a return path to the source then this current flow will very quickly eliminate any sort of potential difference. Without a complete closed circuit any current flow will be transient in nature.

It seems earth does act as a conductor although may not be effective return path as in bonding. The current should not flow simply because of the potential difference unless there is a return path. So, in the above example, if the transformer secondary is UNgrounded and person touches the HOT wire, there should be no current flowing through his body.

If the transformer secondary is ungrounded, then you don't have a defined 'hot' wire. As a practical matter, you always have capacitive coupling and leakage current. So if you have your 'ungrounded' secondary then any one of the terminals might be near ground potential, or they all might be at some sort of elevated voltage. If someone then touches one of the terminals/wires, then there might be some transient current flow, and that terminal/wire will quickly drop to ground potential and the current flow will stop.

Sometimes small isolated ungrounded systems are used in operating rooms to reduce the risk of electric shock. You can touch either of the terminals without much current flow. In large ungrounded systems (say industrial 480V ungrounded delta systems) the capacitive current flow may be enough to cause a significant shock.

-Jon

 

[gar]

171001-2112 EDT

roy167:

I don't believe you know the theory or you would not be asking the question.

If your transformer secondary is connected to a load or no load, and all of the secondary circuit is isolated from anything else (meaning no resistive, capacitive, inductive, or radiation coupling), then you can touch any part of the secondary circuit with one hand and the earth with your other hand and no current will flow and no shock.

.

 

[ActionDave]

It seems earth does act as a conductor although may not be effective return path as in bonding.

The earth does act as a conductor that should never be used as a return path for fault current.

The current should not flow simply because of the potential difference unless there is a return path.

Current will always flow when there is a difference in potential.

So, in the above example, if the transformer secondary is UNgrounded and person touches the HOT wire, there should be no current flowing through his body.

You need one conductor in an electrical system connected to the earth or the hull of a boat or the frame of a car or something conductive before you can name the other one the HOT.

 

[Sahib]

The earth does act as a conductor that should never be used as a return path for fault current.

Some fault current returns through earth anyway.

Current will always flow when there is a difference in potential.

Current does not require a potential difference to exist.

You need one conductor in an electrical system connected to the earth or the hull of a boat or the frame of a car or something conductive before you can name the other one the HOT.

Then both conductors are HOT.

 

[ActionDave]

Some fault current returns through earth anyway.

Current does not require a potential difference to exist.


Then both conductors are HOT.

Fine.

 

[Smart $]

...
Current will always flow when there is a difference in potential.
...

...
Current does not require a potential difference to exist.
...

A potential difference does not require current (infinite impedance), but a current (< infinite impedance) always requires a potential difference. Ohms law is immutable.

 

[GoldDigger]

A potential difference does not require current (infinite impedance), but a current (< infinite impedance) always requires a potential difference. Ohms law is immutable.

The sole exception to the highlighted statement, which is not in conflict with Ohm's Law, is the superconductor. You can have a current with no voltage drop as the resistance of the superconductor is really zero.

 

[oldsparky52]

Well, we both survived the shocking experience although he was a bit jumpy for a bit.

How long before he let you pet him again?

 

[oldsparky52]

Hi, I know the theory. My question still remains

Can earth act as a return path on its own?

Can the current flow merely because there is a potential difference? or for current to flow, there need to be return path to the source? Along with potential difference.

It seems earth does act as a conductor although may not be effective return path as in bonding. The current should not flow simply because of the potential difference unless there is a return path. So, in the above example, if the transformer secondary is UNgrounded and person touches the HOT wire, there should be no current flowing through his body.

The earth (like someone else mentioned) is a reasonable conductor because there is so much of it. The connection to earth is where you have your resistance.

Electricity takes all paths for current, therefore yes the earth will conduct some electricity.

Have you heard about SWER? (Single-wire earth return) The power companies used to do this.

 

[Strathead]

Can the current flow merely because there is a potential difference? or for current to flow, there need to be return path to the source? Along with potential difference.

I didn't look where you were from. Have you ever, rubbed your feet on a carpet and then touched a door knob? Or do you know why lightning strikes? So the answer is that current can "flow" merely with potential difference, but in the cases above, the "flow is short lived until the two potentials equalize.

 

[kwired]

The earth (like someone else mentioned) is a reasonable conductor because there is so much of it. The connection to earth is where you have your resistance.

:thumbsup:

What we call resistance of a ground rod is actually resistance between the rod and earth. Earth is an excellent conductor, but is not so easy to make a low resistance connection to it.

Utility systems have a grounded conductor network that has so many electrodes connected to it that those are considered to be at earth potential for the most part. If you have an isolated supply with just a single electrode to ground it - you won't have as low of resistance through earth as the utility systems have for any possible return path via earth over their entire network.

 

[Smart $]

The sole exception to the highlighted statement, which is not in conflict with Ohm's Law, is the superconductor. You can have a current with no voltage drop as the resistance of the superconductor is really zero.

We are not talking abnormal [here-on-Earth] conditions.

Curious though... with no potential difference, which way does the current flow in this superconductor?