On May 16, 1888, Nikola Tesla gave a lecture describing the equipment necessary to allow for the efficient generation and use of alternating current. Alternating current, in contrast to Direct current, is an electric current which periodically reverses direction. Direct current, on the other hand, only flows only in one direction. Alternating current is advantageous because it is capable of transmitting electric power over long distances. Today, most homes and businesses use alternating current.