alternating current

noun
an electric current that reverses direction at regular intervals, having a magnitude that varies continuously in sinusoidal manner. Abbreviation: ac
Compare direct current.


Origin:
1830–40

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Based on the Random House Dictionary, © Random House, Inc. 2014.
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Collins
World English Dictionary
alternating current
 
n
AC, Compare: direct current a continuous electric current that periodically reverses direction, usually sinusoidally

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American Heritage
Science Dictionary
alternating current  [%PREMIUM_LINK%]     (ôl'tər-nā'tĭng)  Pronunciation Key 
An electric current that repeatedly changes its direction or strength, usually at a certain frequency or range of frequencies. The term is also used to describe alternating voltages. Power stations generate alternating current because it is easy to raise and lower the voltage of such current using transformers; thus the voltage can be raised very high for transmission (high voltages lose less power as heat than do low voltages), and lowered to safe levels for domestic and industrial use. In North America, the frequency of alternation of the direction of flow is 60 Hz, or 60 cycles per second. In other parts of the world it is 50 Hz. Compare direct current. See Notes at current, Tesla.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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American Heritage
Cultural Dictionary
alternating current (AC)

An electric current in which the flow reverses periodically. (Compare direct current (DC).)

Note: In the United States, most household current is AC, going through sixty reversal cycles each second. Electric motors in household appliances are designed to work with current at this rate of reversal.
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Example sentences
The disadvantage is that reverse electrodialysis produces direct current,
  whereas the world runs mostly on alternating current.
It used a semiconductor to control the frequency of an alternating current to
  switch between filaments.
When they plugged one coil into the wall, alternating current flowed through
  it, creating a magnetic field.
He believed systems to distribute electricity to homes and businesses should
  use alternating current.
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