If you were talking about Alternating Current, I would tend to agree with you somewhat, and it would be dependent of certain conditions to be present so that the "Skin effect if you will - isn't negated... However it really depends on the frequency being used as well as the choice of material to be used as the conductor also and of course, we mustn't forget or minimize the importance of EMF as it relates to generating voltage... So voltage is influenced by the EMF generating
V to drive
I through the conductor's cross sectional area of the copper wire...
BUT! We are talking about Direct Current that either flows from the power source through a certain depth (usually the bulk of the cross sectional area of each wire)... We must also consider this: Conductivity is both theoretically and empirically proportional to the cross-sectional area, not the circumference...
Stranded wire is used because it bends more easily, but it has essentially the same conductive properties... Current flows throughout the entire wire... This is easily tested by measuring the resistance of round wires - the resistance will fall quadratically with the radius, indicating that it's the cross-sectional area that matters... This answer is only correct for direct current... The changing magnetic fields introduce eddy currents which yield the skin effect, where current tends to be carried only within the "skin depth" of the wire, which is not proportional to the radius...
Therefore, It is the surrounding magnetic fields, eddy currents & EMF that must be present or not, and how they are formed, manipulated, applied, or removed in a variety of applications that will influence how and where the voltage flows through a conductor... So yes, voltage is one of the most important influences effecting the weld metal composition... However there are equally important factors that must be present via generation or other means in order for voltage to do it's intended role and indirectly effect weld metal composition along with the other equally important factors that must be present... And in the correct proportion with one another, working together because of their co-dependency, or interdependency of each other...
One example is the requirement of EMF, or Electromotive Force, and an applied load via generation or other means to be present in order to produce the necessary voltage to drive the current through the conductor and to a lesser degree, through the
arc plasma which would then create a closed circuit once the
arc has been established is directly influenced by the generation of Electromotive force which in turn directly effects voltage... Read further and you'll understand better...
Electromotive force, also called emf, is the voltage developed by any source of electrical energy such as a battery or dynamo.... Not to be confused with the definition or description of an Electromagnetic field.... The word "force" in this case is not used to mean mechanical force, measured in newtons, but a potential, or energy per unit of charge, measured in volts... Around 1830 Faraday established that the reactions at each of the two electrode–electrolyte interfaces provide the "seat of emf" for the voltaic cell, that is, these reactions drive the current... In the open-circuit case, charge separation continues until the electrical field from the separated charges is sufficient to arrest the reactions... Years earlier, Volta, who had measured a contact potential difference at the metal-metal (electrode-electrode) interface of his cells, held the incorrect opinion that the fact of contact alone (without taking into account a chemical reaction) was the origin of the emf...
In the case of an electrical generator, a time-varying magnetic field inside the generator creates an electric field via electromagnetic induction, which in turn creates an energy difference between generator terminals... Charge separation takes place within the generator, with electrons flowing away from one terminal and toward the other, until, in the open-circuit case, a sufficient electric field builds up to make further movement unfavorable... Again the emf is countered by the electrical voltage due to charge separation. If a load is attached, this voltage can drive a current... The general principle governing the emf in such electrical machines is Faraday's law of induction...
As already mentioned, the conductivity is both theoretically and empirically proportional to the cross-sectional area, not the circumference... An intuitive explanation (for DC or low frequency AC) results from the forces between moving electrons as opposed to static ones... Think of it as Ampere's Law, Maxwell's Equations, or the relativistic nature of electromagnetics... either way, electrons moving in parallel directions attract... So, the actual cross-sectional current distribution would result from the net forces (both attractive and repulsive) of electrons as they course through the wire...
Another point to make is the fact that if the open circuit voltage is improperly set or becomes either too much or too little because of a damaged component(s), the result is a detrimental effect to the weld metal composition... This is not something that usually happens, or is much of a concern with an external powered transformer rectifiers or inverters because of preset OCV, unless a component fails inside the guts of the power source...
Now this is of a concern with engine driven generator welders because the open circuit voltage can be adjusted, and if the incorrect adjustment is made or a component fails also, then this will effect the resulting weld metal composition as well as other factors like geometry, how the use of different welding processes is affected such as with GMAW, or FCAW, MCAW and even GTAW... But, if there's no EMF generated whatsoever by whatever means available, then there will be no voltage present to drive the current through the conductor and across the air gap to land on the parent metal and close the circuit...
So let's break it down further by covering the conduction mechanisms in 2 important conditions... I'll start 1st with metals... A solid conductive metal contains mobile, or free electrons, which function as conduction electrons... These electrons are bound to the metal lattice but no longer to an individual atom.... Metals are particularly conductive because there are a large number of these free electrons, typically one per atom in the lattice... Even with no external electric field applied, these electrons move about randomly due to thermal energy but, on average, there is zero net current within the metal...
At room temperature, the average speed of these random motions is 10 to the 6th power - meters per second.... Given a surface through which a metal wire passes, electrons move in both directions across the surface at an equal rate... As George Gamow wrote in his popular science book, One, Two, Three...Infinity (1947), "The metallic substances differ from all other materials by the fact that the outer shells of their atoms are bound rather loosely, and often let one of their electrons go free.
Thus the interior of a metal is filled up with a large number of unattached electrons that travel aimlessly around like a crowd of displaced persons. When a metal wire is subjected to electric force applied on its opposite ends, these free electrons rush in the direction of the force, thus forming what we call an electric current."When a metal wire is connected across the two terminals of a DC voltage source such as a battery, the source places an electric field across the conductor... The moment contact is made, the free electrons of the conductor are forced to drift toward the positive terminal under the influence of this field. The free electrons are therefore the charge carrier in a typical solid conductor....
Now let's go over the conductive mechanisms as observed with gases and plasma...
In air and other ordinary gases below the breakdown field, the dominant source of electrical conduction is via relatively few mobile ions produced by radioactive gases, ultraviolet light, or cosmic rays... Since the electrical conductivity is low, gases are dielectrics or insulators... However, once the applied electric field approaches the breakdown value, free electrons become sufficiently accelerated by the electric field to create additional free electrons by colliding, and ionizing, neutral gas atoms or molecules in a process that results in what is called "Avalanche breakdown..." The breakdown process forms a plasma that contains enough mobile electrons and positive ions to make it an electrical conductor... In the process, it forms a light emitting conductive path, such as a spark,
arc or lightning...
Plasma is the state of matter where some of the electrons in a gas are stripped or "ionized" from their molecules or atoms... A plasma can be formed by high temperature, or by application of a high electric, or alternating magnetic field as noted above... Due to their lower mass, the electrons in a plasma accelerate more quickly in response to an electric field than the heavier positive ions, and hence carry the bulk of the current... The free ions recombine to create new chemical compounds (for example, breaking atmospheric oxygen into single oxygen [O2 → 2O], which then recombine creating ozone [O3])...
A similar result happens with some of the elements that make up the chemical composition that is cellulose reacting when an electric field is applied to it... The cellulose is now a vaporized substance due to the heat caused by the resistance within the electrode as well as being exposed and making contact with the plasma - literally cooks the cellulose to a sort of gaseous state which is sometimes named a gas vapor along with the heat of the plasma & the
arc energy being produced... The chemical composition that existed when the Cellulose was still a solid is no longer present... Once it's broken down to a total separation of the elements which made up the composition, the free ions from those separated elements do recombine to create new chemical compounds also... So now let's continue to explore
An electrical voltage difference is sometimes called an emf... The points below illustrate the more formal usage, in terms of the distinction between EMF and the voltage it generates:
1.) For a circuit as a whole, such as one containing a resistor in series with a voltaic cell, electrical voltage does not contribute to the overall EMF, because the voltage difference on going around a circuit is zero... (The ohmic IR drop plus the applied electrical voltage is zero. See Kirchhoff's Law)... The EMF is due solely to the chemistry in the battery that causes charge separation, which in turn creates an electrical voltage that drives the current...
2.)For a circuit consisting of an electrical generator that drives current through a resistor, the EMF is due solely to a time-varying magnetic field that generates an electrical voltage that in turn drives the current... (The ohmic IR drop plus the applied electrical voltage again is zero... See Kirchhoff's Law)
3.)A transformer coupling two circuits may be considered a source of EMF for one of the circuits, just as if it were caused by an electrical generator; this example illustrates the origin of the term "Transformer EMF"...
4.)A photodiode or solar cell may be considered as a source of emf, similar to a battery, resulting in an electrical voltage generated by charge separation driven by light rather than chemical reaction...
5.) Other devices that produce emf are fuel cells, thermocouples, and thermopiles...
In the case of an open circuit, the electric charge that has been separated by the mechanism generating the EMF creates an electric field opposing the separation mechanism... For example, the chemical reaction in a voltaic cell stops when the opposing electric field at each electrode is strong enough to arrest the reactions... A larger opposing field can reverse the reactions in what are called reversible cells...
The electric charge that has been separated creates an electric potential difference that can be measured with a voltmeter between the terminals of the device... The magnitude of the EMF for the battery (or other source) is the value of this 'open circuit' voltage... When the battery is charging or discharging, the EMF itself cannot be measured directly using the external voltage because some voltage is lost inside the source... It can, however, be inferred from a measurement of the current I and voltage difference V, provided that the internal resistance r already has been measured: ℰ = V + Ir...
I can continue with more but I believe the case has been made by me to show that although voltage has obvious influence to indirectly influence the weld metal composition... Without ElectroMotive Force or EMF present in a variety of examples to generate Voltage... No EMF = No or insufficient Voltage to drive Amperage or Current and if there's no current available then Voltage is moot... I'll stop here because the game is coming on soon if it isn't on already.
Respectfully,
Henry
