I've been trying to hash this problem out with some friends of mine, but we haven't been able to find a satisfactory answer: Tesla coils are (in an extremely basic sense) like a transformer. There are two coils of wire... the first one having a large current and not-so-large voltage. The second coil has many more turns, so you end up with a large voltage and not-so-large current. Of course, total power (I*V) remains -in a perfect universe- unchanged. The secondary coil, having high voltage, can make some great sparks. Perfect for science museums and sci-fi movies. However, back in the day, Tesla intended these coils to act as wireless power transmitters. And indeed they can do just that over short distances. Like an antenna, the secondary coil of the Tesla coil can set up EM waves that propagate. So here is my question: for power transmission... why do you need high voltage? I understand that you of course need high *power*, but if the power is unchanged going from the first coil (big I, small V) to the second coil (small I, big V), what's the benefit? Is the high voltage able to set up EM waves better than a high current can? Why would that be?