Their two theories on power distribution couldn’t be more mutually exclusive. As divisive as their perspectives on electrical current was, so was their relationship. Tesla worked for Edison in the latter part of the 19th Century. When Tesla told Edison that he could easily redesign Edison’s concepts, Edison reportedly told Tesla, “there’s fifty thousand dollars in it for you—if you can do it”. Tesla worked for several months on his concept. When inquired about Edison’s $50,000 offer, Edison reportedly told him he was joking.
Whether or not that is true, both of their power distribution theories were correct.
Well, AC is easy to generate from turbines, as you’ve just seen. Rotating coil-and magnet devices always produce AC, and in order to get DC from this, rectification and filtering are necessary. These processes can be difficult to achieve with high voltages.
Alternating current lends itself well to being transformed to lower or higher voltages,according to the needs of electrical apparatus. It is not so easy to change DC voltages. Electrochemical cells produce dc directly, but they are impractical for the needs of large populations. To serve millions of consumers, the immense power of falling or flowing water, the ocean tides, wind, burning fossil fuels, safe nuclear fusion, or of geothermal heat are needed. (Nuclear fission will work, but it is under scrutiny nowadays because it produces dangerous radioactive by-products.) All of these energy sources can be used to drive turbines that turn AC generators.
Direct currents, at extremely high voltages, are transported more efficiently than alternating currents. The wire has less effective resistance with DC than with AC, and there is less energy lost in the magnetic fields around the wires.
Direct-current high-tension transmission lines are being considered for future use. Right now, the main problem is expense. Sophisticated power-conversion equipment is needed. If the cost can be brought within reason, Edison’s original sentiments will be at least partly vindicated. His was a long view.
Tesla pointed out the inefficiency of Edison’s direct current electrical powerhouses that have been build up and down the Atlantic seaboard. The secret, he felt, lay in the use of alternating current, because to him all energies were cyclic. Why not build generators that would send electrical energy along distribution lines first one way, than another, in multiple waves using the polyphase principle?
Edison’s lamps were weak and inefficient when supplied by direct current. This system had a severe disadvantage in that it could not be transported more than two miles due to its inability to step up to high voltage levels necessary for long distance transmission. Consequently, a direct current power station was required at two mile intervals.
Direct current flows continuously in one direction; alternating current changes direction 50 or 60 times per second and can be stepped up to vary high voltage levels, minimizing power loss across great distances. The future belongs to alternating current.
Nikola Tesla developed polyphase alternating current system of generators, motors and transformers and held 40 basic U.S. patents on the system, which George Westinghouse bought, determined to supply America with the Tesla system. Edison did not want to lose his DC empire, and a bitter war ensued. This was the war of the currents between AC and DC. Tesla -Westinghouse ultimately emerged the victor because AC was a superior technology. It was a war won for the progress of both America and the world.