alternating current

noun

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

alternating current

noun

1. a continuous electric current that periodically reverses direction, usually sinusoidally AC Comparedirect current

alternating current

/ ôl′tər-nā′tĭng /

1. 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.
2. Compare direct currentSee Notes at current

alternating current

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

Notes

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.

Word History and Origins

Origin of alternating current¹

First recorded in 1830–40

Example Sentences

Researchers used what is called "transcranial alternating current stimulation" to modulate brain activity.

From Science Daily

One of the first West Coast reinforced concrete structures, the steam plant originally powered the Interurban Railway between Seattle and Tacoma and supplied direct current for Seattle streetcars and alternating current for Georgetown.

From Seattle Times

Once the construction is completed, it will convert 1,250 megawatts of clean energy from direct current to alternating current power that will be fed directly into the state's power grid.

From Reuters

The Boat Time YouTubers have invested in a more efficient inverter, which turns the direct current generated by their solar panels into the alternating current used by the grid.

From BBC

The transmission line’s direct-current section allows efficient, long-distance electricity transfer with no tie-ins to other power lines, while the alternating current segment is less efficient but connects to the rest of the grid.

From Seattle Times