An Introduction to AD/DC

Aaron Foyer
Introduction to AC and DC currents

Alternate current (AC)

The electric charge changes periodically reversing direction

Alternating currents are created using a loop of wire is spun inside a magnetic field which induces a current along the wire, known as an alternator.

Applications: High voltage power transmission, wind turbines, car motors, and appliances

Technology champion: While the first alternating current was created by Hippolyte Pixii, Nikola Tesla invented the first AC motor, and developed its transmission and distribution technology


  • Easier to transmit power at high voltages
  • AC generators are simpler than DC generators
  • AC motors are cheaper and simple in construction


  • Interference with communication lines
  • Requires more insultation for safe handling
  • Prone to heating and sparking

Direct current (DC)

The flow of electricity is one direction only, operating at the same voltage output throughout

Batteries provide direct currents, generated from a chemical reaction. Direct currents can also be converted from alternating currents using devices like a commutator or a rectifier.

Applications: Cell phones and laptops, flat-screen TVs, electronic vehicles, fuel and solar cells

Technology champion: Edison was the first to develop direct currents. He also invented the light bulb, the phonograph, an early movie camera, and an alkaline storage battery.


  • Better for transmitting over long distances
  • More suitable for electronic circuits
  • Can be stored in a battery or energy storage
  • Distribution / transmission is less expensive


  • Generators are more complex than AC generators
  • DC machines are more complex than AC machines

The War of the Currents: AC vs DC

In the 1880s and 1890s, Edison and Tesla rivaled competing electric power transmission systems. Westinghouse, using Tesla’s technology, beat out the Edison Electric Lighting Company. Both technologies are now used widely across our society for a range of different purposes.