Hey all - -newbie here. I have a question about AC. I understand the idea changing polarity. What about changing direction? Does AC come from ground then from its positive? If that makes any sense - if I have a circuit, an AC power supply with a positive and negative, does the current flow reverse directions? What about high voltage transmission lines? What I am asking I think is how "far" can AC travel?

Sidebar - am I right in assuming a capacitor is there to make up for the switch in polarity direction to keep a smooth current going?

Thanks!

 

AC = Alternating current, as in alternating/change in direction of current every half cycle.!
A capacitor across an AC power supply/source can pass a high degree of current when the C value is relatively high.
e.g. It is used to conduct AC current to a 1ph motor start winding, it also provides a phase shift in the winding.
As to power lines, they use very high voltage in order to maintain low current, now if the distance is great, DC transmission is preferred.

 

Signal polarity is referencing to the direction current will flow in a conductor. Consider an AC signal connected to a diode, since the diode will only conduct in one direction (ignoring leakage), half the wave will be clipped. If you reverse the diode, the other half will be clipped. If there is no diode, the current will "move" back and forth assuming there is an equal impedance in both directions as well as congruent positive and negative voltage portions of the signal. The principal of reactance becomes important because the voltage / current relationship of inductors and capacitors are no longer linear like a resistor. This expands to the concept of real and reactive power as some arrangements can capitalize on the current already "present" instead of having been dissipated as heat so less real power is consumed.

Please note this is an intuitive response and will not replace a mathematical analysis.

 

Ok makes some sense - so let’s say for example any electronic device in my home. The AC travels from the pole in the item (not concerned about polarity) and then all the way back to the transformer on the street or to the input to my house?

 

Ok makes some sense - so let’s say for example any electronic device in my home. The AC travels from the pole in the item (not concerned about polarity) and then all the way back to the transformer on the street or to the input to my house?

Can you rephrase your question?

 

Hey all - -newbie here. I have a question about AC. I understand the idea changing polarity. What about changing direction? Does AC come from ground then from its positive? If that makes any sense - if I have a circuit, an AC power supply with a positive and negative, does the current flow reverse directions? What about high voltage transmission lines? What I am asking I think is how "far" can AC travel?

Sidebar - am I right in assuming a capacitor is there to make up for the switch in polarity direction to keep a smooth current going?

Thanks!

Yes, the AC current (electrons in wires) changes direction in the wire but it only travels a very tiny distance, then reverses, so the average current movement is zero from transformer to house is zero. What moves from transformer to house is electrical energy/power. The physical movement of current is usually not much of a factor in actual electrical energy transfer.

 

Ok - i think I get that. I thought it travelled an incredible amount of distance in a short time.
So if it’s reversing back and forth, even a short distance, how does it keep “moving” forward? Like how does it complete a circuit if it seems it doesn’t really move? I know this is incredibly basic. I respect your patience with me.

 

Yes, the AC current (electrons in wires) changes direction in the wire but it only travels a very tiny distance, then reverses, so the average current movement is zero from transformer to house is zero. What moves from transformer to house is electrical energy/power. The physical movement of current is usually not much of a factor in actual electrical energy transfer.

So we can say the electrons act as one big Newton's Cradle coupling momentum from one adjacent electron to the next?

 

So we can say the electrons act as one big Newton's Cradle coupling momentum from one adjacent electron to the next?

No, electrons don't transfer the electrical energy in the circuit. When electrons transfer energy, things usually get hot at those spots. For a heater element that's good, for a power line that's bad so we size the wire to reduce electron energy coupling to a some satisfactory amount to reduce I/R losses.

 

No, electrons don't transfer the electrical energy in the circuit. When electrons transfer energy, things usually get hot at those spots. For a heater element that's good, for a power line that's bad so we size the wire to reduce electron energy coupling to a some satisfactory amount to reduce I/R losses.

What is responsible for the transfer of energy?

 

What is responsible for the transfer of energy?

You asked but I tried to stay away from this: https://forum.allaboutcircuits.com/threads/the-big-misconception-about-electricity.183285/

 

Hey all - -newbie here. I have a question about AC. I understand the idea changing polarity. What about changing direction? Does AC come from ground then from its positive? If that makes any sense - if I have a circuit, an AC power supply with a positive and negative, does the current flow reverse directions? What about high voltage transmission lines? What I am asking I think is how "far" can AC travel?

Sidebar - am I right in assuming a capacitor is there to make up for the switch in polarity direction to keep a smooth current going?

Thanks!

This is insightful, certainly worth watching carefully:

 

Prepare yourself for some questions as soon as I assimilate that information into my collective.

 

Prepare yourself for some questions as soon as I assimilate that information into my collective.

Ask on that thread. At first don't question, just assimilate.

 

Вы говорите, что ток — это электроны, а как насчет ионов?

 

Ask on that thread. At first don't question, just assimilate.

Ok but please note you will be the first to be bombarded with questions

 

Ok but please note you will be the first to be bombarded with questions

I've done it many times before but it's takes a while to change your intuition about electrical energy.

 

I've done it many times before but it's takes a while to change your intuition about electrical energy.

Have you written any literature on the subject?

 

Вы говорите, что ток — это электроны, а как насчет ионов?

Sorry, but this is an English language only forum. You can use a translation site if you don’t know English to post your comments.

 

Have you written any literature on the subject?

No, there are tons of good websites, EE and physics books that go into the centuries old details. I don''t have the patience or desire to be a teacher.


https://books.google.com/books?id=U...rs (current) are the energy carriers.&f=false



The strange thing is there is nothing in modern circuit theory that says the charge carriers (current) are the transmission energy carriers. Most people get the idea from bad analogies, not formal training. Current is an important part of the equation as a system and things like AC current are a hell of a lot more intuitive when you put current in its proper place within the energy transfer equation.

https://learn.sparkfun.com/tutorials/what-is-electricity/all