ECE101 – Basic Electrical and Computer Engineering

If you’ve studied the history of electricity at all, you have certainly heard of The War of the Currents.  Edison wanted DC current for power distribution, Tesla wanted AC current.  After quite the dirty little fight, Tesla came out on top with his AC current.  But why?  Despite all the arguments and under handed tactics to persuade the public, it came back to Ohm’s law to decide who ultimately was the winner.

If all wires were superconductors, there wouldn’t be an issue using DC power.  But, in reality, copper wire has a finite resistance.  And as we know from looking at ohm’s law, there has to be a voltage drop across the wire to move a set amount of current through.  As the current increases, the voltage drop increases.  In reality, a run of less than a hundred feet can have a significant voltage drop at the load. So, we take a quick glance at the power equation and can come up with a simple solution.
 

All we care about is power at the end. And as is obvious, it doesn’t matter if most of that power is because of high voltage or high current. So by increasing the voltage, we get a dual benefit. First is that we don’t have to move as much current, so there is a smaller voltage drop. Second is that the voltage drop is a smaller percentage of the overall voltage.

Yet we don’t want to have kilovolt lines coming into our house because of the obvious danger. This is where AC power is the clear winner. Whereas it is difficult and lossy to convert DC voltages, AC voltage merely requires a transformer, both easy and relatively efficient. So power companies create their power, transform it up to extremely high voltages for transmission over long distances, and then slowly step it down to the more reasonable and safe voltage level used in your home.

That’s basically it. The simple ability to transform an AC voltage put it head and shoulders above DC in the War of the Currents and won because of it.