What did Nikola Tesla invent in 1888?

Answer 1

In 1888 Tesla designed the first practical system of generating and transmitting alternating current for electric power. The American rights to this epoch-making invention were bought by the American inventor George Westinghouse, who demonstrated the system for the first time at the World's Columbian Exposition in Chicago. Two years later Tesla's alternating-current motors were installed at the Niagara falls power project.