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We all know the Alternating Current has no definite direction such as forwards or backward but goes both ways, so my question is that as AC flows both ways why does the electrical energy flow only one way? |I apologize in advance if my question is too stupid.

Safiul
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    You have to look at both the polarity of the voltage AND the current: moment-to-moment https://electronics.stackexchange.com/questions/574114/how-does-power-factor-show-itself-in-this-data-from-sensor-readings/574122#574122 – DKNguyen Jul 07 '22 at 16:38
  • It doesn't flow only one way - even for some DC circuits (which utilize reactive components such as inductors and capacitors.) I suggest studying [DC](http://www.ibiblio.org/kuphaldt/electricCircuits/) theory first, then AC. – rdtsc Jul 07 '22 at 17:05
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    Energy does not "flow". Energy is the ability to do some work. This ability is stored in the current existence itself, no matter which direction. Think of flow of water - if the water is still, it can't perform any work. But if it moves - no matter which direction, a properly designed mechanism can extract it's energy to perform some work. – Eugene Sh. Jul 07 '22 at 17:18
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    @EugeneSh., energy is transferred from the generator to the load...I don't see any problem with calling this "flow". – The Photon Jul 07 '22 at 17:50
  • @ThePhoton "Flow" implies some "particles" of energy moving around. There are none. There are particles *having* energy though, which are flowing. – Eugene Sh. Jul 07 '22 at 18:02
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    @EugeneSh., I disagree --- we say things flow even when we consider them as continuous rather than particulate. Certainly people were saying that water "flows" long before they understood that water is composed of particles. And in classical EM, which is still what we as engineers use to model many (probably most) EM phenomena, we have energy transfer without any particles. – The Photon Jul 07 '22 at 18:05
  • @EugeneSh. So the energy flows with the water flow. – Solar Mike Jul 07 '22 at 19:31
  • @SolarMike No. The water can just move in waves back and forth and not flow anywhere. The energy is *stored* in this oscillation. – Eugene Sh. Jul 07 '22 at 19:52
  • @EugeneSh. The water does not go back up the hill to the Grande Dixence - pipe is big enough though at 4m diameter and about 9.9m^3 a second… so no waves and a guaranteed flow. – Solar Mike Jul 07 '22 at 20:04
  • simple answer: there is less resistance for the energy to go into the lightbulb than back into the generator. – dandavis Jul 07 '22 at 20:26
  • @EugeneSh. I've never seen anyone have any problem with treating e.g. heat flux as the flow of energy. I don't see why this should be any different. – Hearth Jul 08 '22 at 00:51
  • @Hearth It is not a problem if one understands exactly what it means. This question is the evidence of the opposite. The simplified term is taken literally and is mixed up with a similar term. – Eugene Sh. Jul 08 '22 at 03:25
  • Consider the EM fields carrying energy, check the direction of Poyting Vector. – Mitu Raj Jul 08 '22 at 05:49

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Energy 'flows' from the source to the load because there is more power on average transferred to the load (assuming the load is reactive, a resistive load will just absorb power). Either way this is demonstrated in the graph below, the power sometimes goes negative when the current times voltage switches directions, but overall the power is positive transferred to the load. And over time the energy delivered to the load goes up, even if you do have a cyclic nature to the current and voltage.

enter image description here
Source: https://meettechniek.info/measurement/theory-definitions.html

Voltage Spike
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Maybe an analogy may help.

If you slap my face back and forth, your hand flies both ways, but the bad energy flows from you to me in either case.

OK, so maybe that was a bit too intense. Let's try a different analogy.

Do you remember the old top-loaded washing machines with a cone in the middle? While washing clothes, the cone alternates direction: it turns clockwise and then counter-clockwise. In either case, energy flows from the cone to the water. Why? Because in one case the torque and the speed are both clockwise; in the other case the torque and the speed are both counter-clockwise. When the speed and the torque are both clockwise (positive), their product (power) is positive: it flows from the cone to the water. When the speed and the torque are both counter-clockwise (negative), their product (power) is also positive: it flows from the cone to the water (negative x negative = positive).

Davide Andrea
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If there is a reactive element in the circuit energy is first stored to the reactive element then it is released from the reactive element so you can say that energy has 2 directions now as well.

Miss Mulan
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    Reactance is neither necessary nor sufficient to answer the question, and I don't think this (debatable) point sheds any useful light on the matter. -1 – TypeIA Jul 07 '22 at 18:52
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    If there isnt any reactive element in the circuit energy is just wasted as heat on the resistor.The elements that store and release energy are reactive elements. – Miss Mulan Jul 07 '22 at 19:00
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    Irrelevant: a heater, or an incandescent light, are examples of purely resistive devices in which AC does useful work rather than "canceling out to 0" as in the question. – TypeIA Jul 07 '22 at 19:19