Ruthless,
the fist thing i was taught was ohms = resistance. the second, volts times amps = watts.
in other words, if dc current will not travel long distances with 0 ohm wiring, why not?
First things first. Go back to Ohm's Law. You've stated the formula for watts as a function of voltage. But what is voltage?
V = IR (amperage * resistence).
If you have zero resistence then you have zero voltage.
Power, stated in watts is:
P = I^2 R(amperage squared times resistence). No resistence no power. No power no work.
Why can't you have a conductor with zero resistence? Because voltage is really electrons traveling through the conductor. They are (obviously) electrically charged. They are alternatively repelled by each other and attracted to the positively charged metal ion lattice in the conductor. They don't travel in a straight line from Point A to Point B - they wander. It's a lot more complex in E&M theory but that's resistence. If you get rid of the cause, electric and magnetic fields, you don't have electricity...but you do have no resistence (there's nothing to "resist"
).
The "sine wave" is really just an electrical trace on an oscilloscope of AC voltage or amperage. Its a graphical image of the phase, direction and magnitude of the current. It looks like a series of the letter "S" laying on their sides.
It shows the voltage building up from zero to peak (positive) voltage and then decaying back to zero and down the slope to peak (negative) voltage as the current switches directions in the conductor. They voltage alternates (thus AC - alternating current) 360 degrees peak-to-peak as the commutator in the generator rotates through 360 degrees. If you slide the trough of one half of the cycle over so that its two ends connect with the two ends of the top half of the cycle you'd have a 360 degree elipse.
Why did AC win out over DC for long distance transmission?
Back to Ohm's Law. P=I^2 R
That's power in once sense but it is also a way of measuring line loss in watts. Obviously you don't want to have a lot of line loss when you are delivering your product, electricity, to your customers. Someone has to pay for that inefficiency - that "someone" is the customer.
AC is transmitted at high voltage and low amperage. In our power loss equation amperage is squared. So you want to keep amperage as low as possible during long line transmission. It's a fairly easy task to generate high voltage low amperage AC current.
Unfortunately, it is difficult and inefficient to try to force DC out at high voltage and low amperage. DC wants to come out just the opposite - high amperage and low voltage. And there's the rub - the line loss is a function of the square of the amperage.
