Alternating current

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An alternating current (AC) is an electrical current whose magnitude and direction vary cyclically, as opposed to direct current, whose direction remains constant. The usual waveform of an AC power circuit is a sine wave, as this results in the most efficient transmission of energy. However in certain applications different waveforms are used, such as triangular or square waves.

Alternating current (AC) and direct current (DC) are the 2 main types of currents used in electrical circuits.


Alternating current is the most useful type of electrical current in many contexts, given that

  • it loses far less power over long electrical lines[verification needed]
  • it is the most used system as a result
  • given that it's the standard system used in electrical mains power, it is the most practical system to adopt in the domestic electricity system as well.[verification needed] Although power can be generated completely off-grid, there is an advantage to transfering/sell off surplus electricity to the national power companies; ie via net metering. Adopting AC power as the standard, allows the use of less equipment (ie power inverter), also there is no 10% power loss due to the use of this inverter.
  • Power lines can be thinner to than comparable DC lines. In practice, ie 12 gauge AC wire can be used, while 10 gauge DC wire would be required. When extrapolating the wiring problem into practice ie in a lightining situation, we see that on AC, 8 lights can be powered, and only 3 on DC[1]


One negative side of AC power is that many different standards have developed around the world. AC power can run at various frequencies, and some countries use other frequencies than others. The "standard" type to use is 230V/50Hz,[2] which is more efficient but more dangerous than the 110 V used in the USA. Caution is always needed with electricity, and the higher the voltage, the more important are safety measures, in case of the unexpected.

Use in domestic energy systems

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Optional comment:

Obviously, pure AC domestic energy systems and DC domestic energy systems can be set up. Besides this, AC-DC hybrid energy systems can also be used.


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