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The flow of charge in an AC circuit?

In an AC circuit,
do the electrons go all the way around the circuit then reverse their direction and go back all the way around?

Or do they oscillate in a fixed position (the electrons do not move around the whole circuit)?

Also how is the energy transfered to the components if they do oscillate?

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(edited 9 years ago)
Original post by MeZala
In an AC circuit,
do the electrons go all the way around the circuit then reverse their direction and go back all the way around?

Or do they oscillate in a fixed position (the electrons do not move around the whole circuit?

Posted from TSR Mobile


If it's normal "pure" AC they oscillate very slightly about a fixed position. They don't move around the whole circuit.
Reply 2
Original post by MeZala
In an AC circuit,
do the electrons go all the way around the circuit then reverse their direction and go back all the way around?

Or do they oscillate in a fixed position (the electrons do not move around the whole circuit?

Posted from TSR Mobile


They definitely oscillate, i.e. their direction reverses however many times a second. I seem to recall that they do drift however despite this and so do eventually complete a circuit, although I can't see how this would work.

So probably the second option. Definitely not the first, I'm not sure how that idea would work with a fixed frequency.
Reply 3
How is the energy transfered to the components if they oscillate?

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Original post by MeZala
How is the energy transfered to the components if they oscillate?

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The same way as with DC.
Why do you think it would be different?
Reply 5
Original post by Stonebridge
The same way as with DC.
Why do you think it would be different?


In DC the electrons flow around the circuit carrying joules of energy to the component.
In AC the electrons oscillate at a fixed point, the electrons do not flow around the circuit, so how will the joules of energy reach the component?

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Original post by MeZala
In DC the electrons flow around the circuit carrying joules of energy to the component.
In AC the electrons oscillate at a fixed point, the electrons do not flow around the circuit, so how will the joules of energy reach the component?

Posted from TSR Mobile


The electrons (or charge carriers) still flow through the component in AC, they just don't always flow in the same direction.
Imagine you have a lamp, a battery, and two wires.
You connect the left wire to the left terminal of the lamp and the right wire to the right terminal. The lamp lights. You then connect the wires round the other way to reverse the current. The lamp lights. You do this swap of wires once every second. The lamp always lights. It doesn't matter which way the current flows and it doesn't matter if you switch the direction of travel of the current once a second or even 50 times a second. The lamp still lights. Energy is transferred from the battery to the bulb very nearly instantly. As soon as the connection is made. You don't have to wait for the charges to actually flow from the battery to the lamp. All that needs to "flow" to the lamp is the electric field from the battery, and this travels at the speed of light.
Reply 7
Original post by Stonebridge
The electrons (or charge carriers) still flow through the component in AC, they just don't always flow in the same direction.
Imagine you have a lamp, a battery, and two wires.
You connect the left wire to the left terminal of the lamp and the right wire to the right terminal. The lamp lights. You then connect the wires round the other way to reverse the current. The lamp lights. You do this swap of wires once every second. The lamp always lights. It doesn't matter which way the current flows and it doesn't matter if you switch the direction of travel of the current once a second or even 50 times a second. The lamp still lights. Energy is transferred from the battery to the bulb very nearly instantly. As soon as the connection is made. You don't have to wait for the charges to actually flow from the battery to the lamp. All that needs to "flow" to the lamp is the electric field from the battery, and this travels at the speed of light.


So a set of electrons travel from the positive terminal to the negative terminal, and another set of electrons travel from the negative terminal to the positive terminal (the opposite direction) simultaneously.

Is the electruc field like voltage?

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Original post by MeZala
So a set of electrons travel from the positive terminal to the negative terminal, and another set of electrons travel from the negative terminal to the positive terminal (the opposite direction) simultaneously.

Is the electruc field like voltage?

Posted from TSR Mobile



Electrons oscillate about their mean position in AC. They don't travel from one terminal to the other. They just move a little bit one way and then a little bit the other way.

The applied voltage (pd) from the battery to the circuit applies an electric field to the wire. It's the electric field that moves the electrons and provides them with the energy they give to the components (eg heat to the resistor.) Heat is produced in a resistor irrespective of which way the electrons move in it.
Reply 9
Thank you very much, I have a much better understanding of alternating current now.

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