Why did alternating current beat Edison's direct current?
The famous fight was nastier than the legend, but the winner was decided by simple arithmetic about wires: at low voltage, power cannot travel far.
▶ Start the storyAlternating current won because of one fact about wires: you can send the same power much farther if you use a higher voltage, and in those days only alternating current could easily change voltage.
Thomas Edison's pioneering electric utility used a low 110-volt direct current supply. Because the system ran at 110 volts from plant to customer, generating plants had to sit in the middle of population centers and could supply customers less than a mile away. Alternating current had a key advantage: transformers could step the voltage up for transmission and down again for homes and businesses. With high voltages, one central station could supply circuits up to 7 miles long.
Edison's DC
- 110 volts from plant to customer
- Plants in the middle of cities
- Reach under a mile
AC with transformers
- Voltage stepped up for transmission
- Stepped down for homes
- One station serves circuits up to 7 miles
Why is high voltage better? For the same power, higher voltage means lower current, and since energy losses in a wire are proportional to the square of the current, halving the current cuts the loss by a factor of four. A thin, cheap wire can carry power a long way.
The fight got ugly. Harold Brown claimed AC was more dangerous and publicly killed animals to show it, with technical help from Edison Electric. Meanwhile Edison's own company president warned that an all-DC system could not serve small towns and even mid-sized cities. In 1892 Edison Electric merged with its largest competitor to form General Electric, and Westinghouse, which had licensed Nikola Tesla's motor patents, won the contract for the Niagara Falls hydroelectric project. The war was over, and AC had won.
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Recap
AC won because a transformer can raise its voltage for transmission, and higher voltage means lower current and far less loss in the wire.
💡 A trick to remember it · Raise the volts, shrink the amps, and the wire loses far less on the way.
Surprising fact · Edison's own company president warned that an all-DC system could not serve small towns.
Sources (4)
No source, no claim. Every fact in this lesson (20 claims) cites at least one of these.