Early developments in electric power technology helped industries to harness the power of electricity and transport it from place to place. In the early 1800s, the work of Nikola Tesla led to the development of alternating-current (AC) and direct-current (DC) technologies, including batteries and cross-country power transfer. The experiments of Georg Simon Ohm led to his 1927 discovery of Ohm's Law, which measures electrical current and opened the door for increased complexity in electrical circuits.