False. Pure copper (Cu-ETP) is standard. CCA (Copper-Clad Aluminum) is not copper; it requires a 2-step larger size. And "tinned copper" is for marine/corrosive environments but has identical ampacity.
Prevents cables from overheating and starting fires. copper cable sizing
False. For AC power (50/60 Hz), skin effect is negligible at typical sizes (< 250 kcmil). A 10 AWG solid and 10 AWG stranded have the same ampacity. Stranded is just easier to bend. copper cable sizing