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Sitemap Alternating current (AC) Diagram

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Conductor and Insulator Properties

An electrical current (the movement of electrons) happens when there is a potential difference (voltage) between the ends of a conductor.

Conductor atom

Insulator atom

Basic Electricity

Conductor atom

Single electron in outer orbit

Insulator atom

Multiple electrons in outer orbit

Direct and Alternating Current

Current flows in one direction. A battery operated flashlight is a very common example of direct current.

Direct current (DC) Diagram

Direct Current (DC)

Alternating Current (AC)

Current flows in both directions. 120 VAC 60 Hz household power is an example of AC current. There are two changes in polarity and two changes in current direction per cycle. The current in 120 VAC  60 Hz changes direction 120 times per second as shown below.

0 deg

0 sec

0 V

120 V Sine Wave

180 deg

1/120 sec

0 V

360 deg

1/60 sec

0 V

120 V

+170 V

0 V

-170 V

Degrees

Time

Voltage

Peak voltage

Nominal voltage

Peak voltage

At 0 degrees the voltage is at 0 volts and starts to rise to a peak voltage of 170 volts at 90 degrees. At 90 degrees the voltage goes back down to 0 volts at 180 degrees. The current then reverses direction and rises to a peak voltage of -170 volts  at 270 degrees. To complete the cycle the current goes back to 0 volts at 360 degrees and the cycle starts over.