AC goes one way in one phase and the opposite way in the other phase, but is going right and to left, or is it only changing the polarity from (-) to (+)?

If light bulbs turn off and on (so fast we don't notice, thanks for the gigantic frequency of electricity) that will mean that it goes one way and then to the other, but how is that possible? I would think that the charge should get stuck if it worked like that.

  • 1
    $\begingroup$ Imagine rubbing back and forth on an object to generate friction. It doesn't matter that you don't go anywhere on average--you still have motion/friction/power dissipation. $\endgroup$
    – zeldredge
    May 26, 2015 at 0:39
  • $\begingroup$ Note that 50/60 Hz is not "gigantic". (For comparison, the fastest I can count out loud is about 10 Hz) $\endgroup$
    – user253751
    May 26, 2015 at 3:01
  • $\begingroup$ The power from the wall outlet is either 50 Hz or 60 Hz depending on where you live. that's not a fast frequency at all. It's quite slow. You don't see incandescent lights oscillating at this frequency because they stay hot while the current changes direction. $\endgroup$
    – DanielSank
    May 26, 2015 at 3:47
  • $\begingroup$ But you might see fluorescent lights flicker, if you have a nice camera. $\endgroup$
    – zeldredge
    May 26, 2015 at 3:52

2 Answers 2


A light bulb wouldn't turn off, because no matter what direction the electricity is flowing through it, it is still electricity. It doesn't gain some anti-electricity effect.

Here is an analogy with water. The water works flowing forwards and backwards. (Although in this example there is a stop.)

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If there is still confusion, however, remember that lightbulbs slowly go out (not instantly, they fade out), so in the short "current switch" time, nothing would happen.

  • $\begingroup$ O so, because circuites must have a loop the charge would work at any direction, thanks I didn't took that fact in mind... $\endgroup$ May 26, 2015 at 1:07

AC is a form of oscillating power, like a jig saw. The generator uses magnetic induction which, as you know has two poles + and - . One hertz, or one rotation creates one complete cycle but one cycle is comprised of both + and - forces.

Also one cycle is considered a sine wave, or sinusoidal wave.

A phase is considered a separate sine wave. If you live in the US, the secondary windings on the transformer that delivers power to your house uses one sine wave that is tapped in the center and is also 180 degrees of phase, which gives the center tap zero potential voltage which is considered the neutral.

Also, voltage and current are fundamentally different things. The voltage is a force carrier, it represents the magnetic induction, it wants to travels at the speed of light, as it is basically electromagnetism. Current is the transfer of mass, which the copper wire contains in a efficient makeup to allow the circuit to work.

If you want to read up the matter see http://www.electronics-tutorials.ws/accircuits/sinusoidal-waveform.html


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