# Homework Help: AC vs DC current Tesla vs Edison

1. May 31, 2007

### shanktank

hey all, another quick question for ya

The modern system for transmission of electric energy using alternating current (AC) originated with an inventor named Nikola Tesla. An American entrepreneur, George Westinghouse, bought the rights to Tesla's system and managed to convince consumers that the system was much better than a rival DC system devised by Thomas Edison. Explain why a DC system cannot use an efficient stepped up voltage for long distance transmission.

ok so i know AC replaced DC with most generation and power distribution and that the wires are cheaper and thinner, and that AC can be stepped up to high voltages using transformers and then stepped down again.... but whats the reason the DC system can't?

2. May 31, 2007

### turbo

You have just made the financial case for AC. Can you figure out why DC voltage potentials cannot be manipulated like AC?

3. May 31, 2007

### shanktank

because its a direct current? lol

4. May 31, 2007

### turbo

If you have AC, you can run it through the primary coil of a step-up transformer, extract the resulting flow from the overwound secondary coil and feed it to a transmission line that does not have to be particularly beefy. You can reverse this process at the transformer feeding your house and result in a 240-260V excursion in the AC, and then reference that center-tap to ground to give two "legs" at your breaker panel that can give you about 125v excursion around ground. How could you propose do do something similar with a DC system? Can you imagine an affordable system to accomplish this with DC transmission (esp. over long distances!)?

5. Jun 8, 2007

### shanktank

still not gettin why the dc can't do this?

6. Jun 8, 2007

### ank_gl

coz DC cant be stepped up or down like AC. u step up AC coz at high voltages and low currents, losses are minimized.
can you think of some way of stepping up DC??
a transformer works bcoz of the alternating nature of AC!!

7. Jun 8, 2007

### shanktank

so is dc just a steady current then?

8. Jun 8, 2007

### esalihm

yes it is, and that is why it is called direct.
alternating current can be altered using transformers and stuff but not DC, I suppose "it is not in its nature..."