With whom did Nikola Tesla feud over whether alternating current or direct current should be used as a electricity supply?

Direct current is not easily converted to higher or lower voltages. Tesla believed that alternating current (AC) was the solution to this problem. Alternating current reverses direction a certain number of times per second (60 in the U.S.) and can be converted to different voltages relatively easily using a transformer.

Edison, not wanting to lose the royalties he was earning from his direct current (DC) patents, began a campaign to discredit alternating current. He spread misinformation saying that alternating current was more dangerous, even going so far as to publicly electrocute stray animals using alternating current to prove his point.

In 1893, General Electric bid to electrify the Chicago World’s Fair (also known as the World’s Columbian Exposition) using Edison’s direct current for $554,000, but lost to George Westinghouse, who said he could power the fair for only $399,000 using Tesla’s alternating current.

That same year, the Niagara Falls Power Company decided to award Westinghouse (who had licensed Tesla’s polyphase AC induction motor patent) the contract to generate power from Niagara Falls. Although some doubted that the falls could power all of Buffalo, New York, Tesla was convinced it could power not only Buffalo, but also the entire Eastern United States.

On Nov. 16, 1896, Buffalo was lit up by the alternating current from Niagara Falls. By this time General Electric had decided to jump on the alternating current train, too.