What is the Science Behind Electric Shock and Grounding?

[Per Oni]

Am going away for a couple of days and therefore can't reply with any kind of proper answer, not ignoring you.

 

[Per Oni]

No need for hydraulic, just electrostatic.

There is both push and pull. In a DC circuit the excessive number of electrons on the negative plate are all pushing against each other's static fields. The positive plate has a massive shortage of electrons and the unbalanced protons in the atoms will attract any available (as from a conductor) electrons. The repulsion and attraction (to ions) of the electric fields of each electron do it all.

The pulses that we see along a conductor(such as on initial connection) are just a localized area where the electrons are compressed together that moves along a conductor at approximately V=c.

DC

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@ DarioC, in the hope you’r still about: Even though you call it electrostatic, when you say there’s both push and pull you are still referring to a hydraulic / mechanical system. Mechanical systems push and pull direct on adjacent neighbours. The problem with this kind of power transport are the huge forces which are involved.

The way I see it is different in that an electric field does the pushing and pulling on each charge.

Now you’r probably going to say: the power supply provides the electrical field. Which is true but an electrical field is conservative and therefore needs to be replenished all the time. So in my case, we must therefore have a traveling electrical field which has to carry the power to a far way load. This must be the case for dc as well as ac.

I hope I do make some sort of sense.

 

[sophiecentaur]

I worry that people don't seem to be drawing a distinction between Field and Potential. It is Potential that is important to consider here. The field varies around the circuit, according to the rate of power dissipation in each part so it would be meaningless to say you have 230V across your supply wires and they are separated by 0.01m so the field is 23000V/m. The potential is 230V and that's what counts.

Any arm waving explanation still needs to keep both feet on the ground of basic theory if it is to work.

 

[DarioC]

Oni,
Do you propose that there is some electric "field" that is somehow not the same as the charges surrounding the individual electrons, and that it travels through the conductor independent of what the electrons are doing? Do I have that correct?

Do you mean there is a charge, field, or potential in an electric circuit that is not caused by the electrons in the conducting material?

DC

EDIT: Ah, I just had a flash of possible comprehension. Are you thinking of a electric field like that associated with a electromagnetic wave moving through "space"?

To my knowledge there is no (electric) field, charge, or potential, independent of that surrounding electrons, present or required in conductive material for the functioning of a basic D.C circuit.

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[Per Oni]

Oni,
Do you propose that there is some electric "field" that is somehow not the same as the charges surrounding the individual electrons, and that it travels through the conductor independent of what the electrons are doing? Do I have that correct?

Do you mean there is a charge, field, or potential in an electric circuit that is not caused by the electrons in the conducting material?.

No this electrical field cannot be seen as independent of the free charges, ie in your example the electrons. That condition must be true as can be seen when we insert (say) a capacitor in the circuit.

EDIT: Ah, I just had a flash of possible comprehension. Are you thinking of a electric field like that associated with a electromagnetic wave moving through "space"?

To my knowledge there is no (electric) field, charge, potential, or current, independent of that surrounding electrons, present in conductive material.

To these questions: I cannot take you any further, although you can google the Poynting vector. Professor Feynman once famously said: "Intuition would seem to tell us that the electrons get their energy from being pushed along the wire……but theory says that the electrons are really being pushed by an electric field, which has come from charges very far away….."

 

[DarioC]

Gee, I thought that was exactly what I was saying. Except that you seem to think there is some EXTRA field and I am saying that the only "fields" there are the ones associated with the electrons themselves. That is all it takes. Again I am talking about a D.C. Circuit.

Feynman is exactly right, of course, but the energy is propagated by the fields of the charges on the electrons themselves, not some extra other "field." The "far away" charge is the massive collection of electrons on the negative plate of the battery.

When you go to other circuits, using varying magnetic fields, as in a generator, this situation is no longer true.

 

[Pythagorean]

Yup, even in a capacitor, the fields come from charges built up on the plates.

 

[sophiecentaur]

Yes that is correct, but that applies to one electron locally. The question I’m asking is: is this electron being pushed in a hydraulic way? My answer is: no they are transported in a way similar as raindrops in a gravitational field.

Remember that, if you want to visualise it this way, it is also being 'Pulled' at the other end of the circuit. At the same time, the positive ion cores of the metal are being pushed and pulled the other way (although they don't move) so the net 'force' on the conductor is zero.

I have a thought experiment in which a shallow tray of mercury has a voltage applied between two opposite sides. Although probably not measurable, the atoms (minus an electron) should move slightly to the negative side, causing the liquid surface to be tilted slightly, whilst electrons move steadily to the positive side.

 

[DarioC]

How interesting SC that I was just now at the library reading a Scientific American article on a new experiment using dual interferometers to see if there is a digital nature to space at the Planck size. The experimenters judge the variations will take place at MHz rates so they will be able to discern them from background low frequency shaking.

Wonder if an interferometer could be used on one end of your tray to see if the level of the mercury goes down when the voltage is applied? That doesn't even sound like an expensive experimental setup? Ah, same problem though with "geologic" shaking.

DC

 

[sophiecentaur]

Interferometry is good at spotting small displacements so I guess it would work.
The force on the mercury would be small as the field would be small. I haven't though of the details but a trough of mercury (resistivity about 10^-6) 100mm long by 10mm wide by 1mm deep would have a resistance of 0.1Ω. With 10A passing, there would be a 1V drop across it - giving an E field of 10V/m. So there would be two forces acting - mg downwards and qE sideways. Where q would be some value of effective positive charge, distributed amongst the mercury and m would be the mass of the mercury. I'm not sure what value of q would apply here but the two forces should give you an idea of the relative gravitational and electric forces - hence the slope of the liquid. Perhaps you could treat each atom separately? I started a fag-packet calculation but I got number overload and I have jobs to do!
Perhaps this needs a new thread. - will do when the mood takes me.

 

[Per Oni]

SC, the forces you are talking about are very real, and are not unlike the ones you will find in discharge tubes. See:
http://en.wikipedia.org/wiki/Electric_glow_discharge#Basic_operating_mechanism
In that article you can see separation of +ve ionic clouds attracted to the negative electrode.

If you come round to doing your mercury experiment, you must also take in account the pinching effect of the magnetic field due to the current. Unfortunately no experiment is ever simple! See:
http://www.df.lth.se/~snorkelf/Longitudinal/node3.html
This is part of a bigger article full of interesting stuff about conduction forces.

 

[sophiecentaur]

Oh I remember the pinch effect. I went to the Culham labs in the mid 60s and they were containing plasma that way. They had a MegaFarad capacitor bank, I seem to remember - and none of your low voltage 'supercapacitors' in those days. This was a whole room full of great cylindrical jobs.
Re your link: at least all the mercury would be liquid!
!