remember maybe a decade ago or so, copper used to be cheaper than aluminum. now it is the other way around, copper is more expensive. Even copper pennies cost more so I heard they are mixed with another metal to make a penny. What caused the change in value and when did it really start happening?In fact, copper has become valuble enough to steal. Some factories which have copper, have had their metals stolen, but outsiders who break into the factories to specifically take the copper. Then the factories started hiring security to prevent intruders from taking the copper.
Actually Ba, aluminum requires a TON of energy to extract. You'll only see aluminum being purified near sources of cheap energy. As for why aluminum being cheaper, it's just more plentiful. It all comes down to scarcity, Plus, there is a lot of demand for copper, which will also drive up the price.
The two metals are a long way apart on the electro-chemical scale. This means that if they come into contact, a small - but significant - voltage will exist between them - completely independent of what currents are actually in the wires. This small voltage causes corrosion of both metals: not good!
aluminum is probably being replaced with plastic and composite materials in such things as airplane bodies and equipment housing. copper's main use is in wiring, and there is no replacement for it (yet)
you didnt even mention the people that break into houses to steal the pipes from the walls. Because copper is much harder to extract, aluminum you just get the bauxite, crush it and put it in water, viola
