The Relationship Between AC & DC
AC and DC are the two main ways of delivering an electric charge. AC is short for alternating current; DC stands for direct current. Both play an important role in powering circuits and devices, but each is more suited to certain applications. There are circumstances where AC is more efficient and less expensive to use than DC, and vice versa.
Other People Are Reading
-
Background
-
DC current was once the primary source of electricity for buildings, motors and other electronics. That changed because of the work of Nikola Tesla (1856-1943). Tesla originally worked for Thomas Edison, whose company was the main builder of direct current systems. While there, in his spare time, Tesla invented the first AC system of motors, dynamos, and transformers. He was unable to persuade Edison to embrace his vision of alternating current as a source of power, and he left the company in 1885. He later sold his patent of an AC system to Edison's rival, George Westinghouse. Tesla's vision eventually won out over Edison's, which is why buildings today are powered by alternating current. Edison's company later became General Electric.
DC Currents
-
Direct currents flow in one direction only and are constant in time. Plotted on a graph, their appearance is of a flat, unvarying line. Batteries produce DC current.
-
AC Currents
-
Alternating currents flow first in one direction and then switch, flowing in the other. They vary it time; on a graph, their form is a sinusoidal wave. The electric plants that power our cities produce AC currents.
In North America, standard AC is 120 volts at 60 hertz -- meaning it changes direction 60 times per second. In Europe, AC is generally 220-240 volts at 50 hertz.
Current Conversions
-
AC currents power buildings, but many electronic devices require DC currents. In such cases, a semiconductor component called a diode is placed inside the device. It serves as a rectifier, converting AC into DC. The diode clips part of the AC wave.
AC vs. DC
-
Michael Faraday (1791-1867) discovered that current is produced when a wire is moved in and out of a magnetic field. This is Faraday's Law of Induction: A changing magnetic field produces a voltage, and the more rapid the change, the bigger the voltage that is produced.
Because of induction, AC currents are less expensive and more efficient to carry over long distances. Induction is why AC currents are used to power buildings. Most motors today are AC, also because of the efficiency of induction. Many electrical devices require DC power to operate, however.
For short distances, low voltages, either AC or DC, are preferred because they can be insulated better. This makes it easier to guard against the circuit becoming damaged or destroyed.
-
