What does AC and DC stand for in the electrical field?
Alternating Current and Direct Current
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Average Current and Discharged Capacitor
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AC stands for Alternating Current and DC stands for Direct Current.
Direct current comes from batteries or solar panels or DC generators, things which make one terminal positive always and the other terminal negative always.
Alternating current comes from AC generators or from transformers connected to AC generators. An alternating current generator produces an alternating voltage, usually approximating a sine wave, where one terminal is positive and the other negative for half of a cycle and then the polarity is reversed and for another half cycle the first terminal is negative and the second terminal is positive. In the USA, the standard AC power frequency is 60 cycles per second (60 Hertz), which means that the polarity reverses 120 times per second.
In the early days of commercial power distribution in the USA, Edison used many DC generators, distributed over a city, to supply power to homes and businesses. The generators were set to produce about 110 volts DC so that when the power reached the users through connecting wires, it was about 100 volts. The voltage drop in the connecting wires made it not feasible to deliver the power over a long distance, hence lots of small generators were distributed across the city.
Then it was determined that if the generators produced AC voltage, the voltage could be applied to step-up transformers for transmission to a neighborhood and then stepped down to the expected voltage of about 100 volts. The result was that the power could be distributed over distance with much less power loss in the connecting wires and so a few large AC generators located away from the city could supply the needed power. This meant less noise, smoke, and coal delivery in the city.
Incidentally, the voltage produced by your cell phone microphone and that applied to your cell phone speaker or earphones is AC. Also, all radio waves used to transmit radio, TV, cell phones, etc. come to the antennas as high frequency AC. It isn’t just used for power distribution