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Direct and Alternating Current

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War of the Currents

War of the Currents

Credit: Jim Henderson
Source: http://commons.wikimedia.org/wiki/File:Forest_Park_electric_tree_jeh.JPG
License: CC BY-NC 3.0

This old electric pole in New York City is no longer in use. It shows that electric poles and electricity have been part of the landscape in the U.S. for a long time. Today, electric poles in the U.S. carry alternating current (AC), but that wasn’t always the case.

The Back Story

  • In the late 1800s—shortly after Thomas Edison invented the light bulb and electricity was first becoming popular—most circuits in the U.S. carried direct current (DC). A European immigrant to the U.S., named Nikola Tesla, worked for Edison and helped to improve Edison’s DC generator.
  • Credit: Wikimedia
    Source: http://en.wikipedia.org/wiki/File:Tesla_circa_1890.jpeg
    License: CC BY-NC 3.0

    Nikola Tesla also played a central part in the development of radio communication [Figure2]


  • Tesla also invented an AC generator and tried to convince Edison to adopt it. However, Edison refused and went on to try to discredit the invention. Tesla found support for his invention from George Westinghouse, a Pennsylvania businessman who was entering the electricity business.
  • Soon, Edison and Westinghouse were engaged in a “war” over which of the two types of current should supply the U.S. with electric power. Despite what many considered to be Edison’s “dirty tricks,” Westinghouse and AC won out.
  • Watch this video to learn more about the war of the currents and the pros and cons of the two types of current:


What Do You Think?

At the links below, explore these issues in more detail. Then answer the questions that follow.

  1. What is the basic difference between direct and alternating currents?
  2. Why was Edison so resistant to the idea of AC over DC power generation?
  3. What “dirty tricks” did Edison use to try to convince people to adopt DC over AC?
  4. Why was AC adopted throughout the U.S. in the early 1900s?
  5. The invention and increasing popularity of electronic devices has led some people to question our continued reliance on AC power. Why?
  6. Today, people are looking for ways to add electricity from alternative sources, such as solar panels or wind turbines, to the electrical grid. Why does AC make this difficult to do? Why would DC make this option more efficient?
  7. What do you think? Will our electrical grid ever change from AC to DC? Why or why not? Reflect on what happened during the war of the currents before writing your answer.

Image Attributions

  1. [1]^ Credit: Jim Henderson; Source: http://commons.wikimedia.org/wiki/File:Forest_Park_electric_tree_jeh.JPG; License: CC BY-NC 3.0
  2. [2]^ Credit: Wikimedia; Source: http://en.wikipedia.org/wiki/File:Tesla_circa_1890.jpeg; License: CC BY-NC 3.0


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