Alternating Current (AC)
Electric current that periodically reverses direction, typically 50-60 times per second (Hz).
Easier to transform voltage levels (step up/down with transformers)
Lower energy loss over long distances
Used in power grids and home appliances
Direct Current (DC)
Electric current that flows consistently in one direction, like from a battery.
Constant voltage and direction
Essential for electronics and digital devices
Used in batteries, solar panels, and electric vehicles
The Current War
Thomas Edison
Championed DC power in the late 19th century. His DC systems powered the first electrical grids in cities like New York.
However, DC couldn't be easily transformed to higher voltages, limiting its transmission range to about 1 mile from the power station.
Nikola Tesla
Developed AC systems that could be stepped up to high voltages for efficient long-distance transmission, then stepped down for safe use.
George Westinghouse backed Tesla's AC system, which won the "War of Currents" due to its superior transmission capabilities.
Modern Applications
Power Transmission
AC dominates power grids worldwide. High-voltage AC transmission (up to 1,100 kV) efficiently moves electricity across continents.
Electronics
All digital devices use DC internally. AC from wall outlets is converted to DC by power supplies in computers, phones, and appliances.
Renewable Energy
Solar panels produce DC power, which is often converted to AC for grid connection. High-voltage DC is becoming popular for long-distance renewable energy transmission.