I recently started working in low voltage electrical repair/upgrades in automobiles. I have a couple interns that i am working with and i truly want to be dam* sure im explaining things properly to them. Me and my boss have had heated discussions on the subject and i believe him to be incorrect on some understanding but as he is 50 years my senior and far more experienced i fear that perhaps it is I that does not fully understand how AC and DC power flows through circuits. I would like to lay out what i think to be true here in the hopes of being corrected by those who know far more than I and perhaps even be given some good documentation on how it all works. I have found some MIT youtube lectures which is where i have gotten much of my information to date. "I have come here in hopes of finding more scientific reasoning and rational as most of what i have found online thus far is conjecture and biased personal opinion from working in the industry with little to no documented backing to there opinions. I work with 12-16V DC current for power and 20hz to 35Khz with AC power. 20-150HZ operating over 16-8ga stranded wire, 150-1500hz on 16-18ga wire, and 1500-35,000HZ on 18-22ga wire. Solid core wire will have greater current capacity than stranded over long runs due to it having less resistance and thus less inductance to reduce the skin effect depth at higher frequencies. solid wire is also cheaper to manufacture and is more durable which is why its used predominantly in houses for electrical power and not so much in cars. DC current does not have frequency and thus skin effect has absolutely no place in the discussion because the electrons travel through the ENTIRE wire and not just on the surface. in that same breath AC current at low frequencies is not effected by skin effect as the skin effect depth is often greater than the diameter of the wire. case in point a 100hz signal traveling on an 8ga wire has a skin depth of nearly double the diameter of the wire and thus skin effect has absolutely no bearing on conductivity. as a wire heats up due to inductance the resistance increases and the usable skin depth lessens along the wire. solid core wire is smaller in diameter than stranded as due to the air pockets in stranded wire it must be larger than solid to retain the same current capacity. does stranded wire share a common skin effect or does each individual strand have its own skin effect occurring? (assuming this is not litz wire) Litz wire is advantageous at very high frequencies as it can carry a far greater load due to each strand having its own skin effect and there by increasing the usable surface area for signal transmission. when using CCA or CCS wire in high frequency transmission (<Ghz range) only the outside of the wire is used and thus there is little to no signal degradation due to the wire not being pure copper. however when dealing with DC currents having CCA or CCS wiring will lead to greater heat increase as the capacitance of the wire is greater and aluminum is 25% less conductive than copper so the CCA/CCS wire would need to be 25% larger than a pure copper wire to carry the same current. also with the increase in heat in the CCA/CCS wire you will loose capacity as your resistance will climb with the heat. OFC wiring has a negligible difference when compared to pure copper wire in both oxidation over time and over all capacity/resistance of the wiring. finally how does soldering a wire effect its specs? say i take a stranded wire and solder it to a stranded wire then i have created a solid wire in between two stranded wires. how does this effect the flow of electrons? does anyone know definitively how the various types of solder effect conductivity?