AC question

While I usually am skeptical of analogies, let me offer one. Consider sawing. To cut through a piece of wood, you can use a band saw or circular saw. You could also use a reciprocal saw such as the kind that has a handle on both ends for which is used by two sawyers taking turns pulling the blade. There are also saws that one person can use by pushing and pulling.

The band and circular saws go only in one direction. The other saws I mention go in two directions. The former ones are dc, the latter ones are ac.

Bill

-- Fermez le Bush--about two years to go.

His explanation was really bad. Here is a simplified but more accurate one.

DC current flows in the same direction, at the same magnitude, constantly. AC current varies it's magnitude and alternates direction, typically going through a full cycle from (0 to +MAX to 0 to -MAX to 0) either 50 or 60 times a second depending on where you are located (speaking strictly about power systems).

Electric current does does work (lights a light, produces heat, or rotates a motor) regardless of which direction it flows, or whether it is direct or alternating. Some of the equipment will be different for AC or DC (particularly motors) and transformers only work with AC.

Ben Miller

Probably better to think of it as others have said, the current lows backwards and forwards through the load doing work in either direction.

Hey when you explain these things you have to forget using Lysergic Acid Analogy;-) non technical or enigineering savy persona can understand these concepts well as they are.

The bests is Phouls ( shame shame :)

The Generator Pulls and Gives Energy with every Oscilation at the rates Ben mentioned. (electromagnetic ~ mechanical turn)...

So' now I trust you can see how it sends a pulse, that expells and retrieves Electrical Energy from the System.

You see Water going down the drain apparently lost forever too, but it is collected in the Sewer & Drain system - the same is achieved in those Electrical Power AC System, and the Utility Collects it in Billings for now........ (teeheehee)

~ Tick Tock ~

This reminds me of the beginner who, having absorbed the notion that a flow of electric current requires a complete circuit, asked "Why does the electricty company bill me when they get the electricity back again?".

The same is true for water, at least in Los Angeles. You pay for the water and then pay for the sewerage. If you can prove that you do not send the water back, the sewerage charge will be reduced.

Bill

-- Fermez le Bush--about two years to go.

I suggest in future you stay skeptical and don't try the analogy thing :-)

Agreed

Not agreed

I'm not qualified to give a response to whether it's accurate or not.

I want to hear: Yes or No; it does/does not go back to the plant, and this is how it does it. I want to know if I lived one light year, or say, an infinity away, and I turned on the light and it took too long to get back to the plant because of the vast distance from the load (if it really goes to the load and back) would that then be in essence DC currect because it's to far to make the cycle back? req

All of the current? you mean none gets used? So on the way back to the plant ( after passing back through the meter) theoretically I could tap into it and get some free currenct? req

What the hell is lysergic acid? :-)

Here we go again... where does it *pull* energy from?

Do they really get it back? are you saying it there is no loss when I use my dryer? req

"reqluq" wrote in news: snipped-for-privacy@corp.supernews.com:

Yes, there is loss, because the dryer converts the electrical energy into heat energy.

---------------------- All the current. Note that current is not power or energy. You can measure the same current in the return that you have going to the load. One of the basic laws is Kirchoff's current law which can be described as "what goes in comes out". This is true at any cross-section of the circuit so one can have a source-line-load-return line loop where the current is the same everywhere.

When you think of supplying a load, you have to consider both voltage and current (which produce power. For example, you could have a 13 volt battery supplying a load resistance of 6 ohms. The wires and battery may have resistance of 0.5 ohms so the total resistance is 6.5 ohms. The current will be 13/6.5 =2A everywhere in the circuit. The voltage across the 6 ohm load will be 6*2 =12V and the voltage drop in the wires,etc will be 0.5*2 =1V. Total 13V. The load power is 12*2 =24 Watts and the source will supply 13*2 =26 watts. The difference is the power loss in the wires (I^2R =4*0.5 =2Watts). Sure you can tap into the wire and add another load- say another 6.5 ohms but the result is that now the current will be 1A and the various powers and voltages will change accordingly. Try two 3V flashlight bulbs in series supplied by two D cells in series (as in a normal flashlight), you will have two very dim lights.

This is true for DC and also for AC (a bit more complicated ). For AC the polarity of the voltage supplied changes every cycle so the current also reverses accordingly. Don't try to mentally follow electrons flowing as for AC they simply wobble around while the energy "flows" at near light speed. Even for DC, the electrons (or other charge carriers) simply drift along lazily and the speed or location of an individual electron is neither of concern nor measurable. --

Don Kelly snipped-for-privacy@shawcross.ca remove the X to answer

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Sure the energy is flowing in and out of the power station but it takes applied energy to make it do that. I.e a gas turbine or diesel prime mover etc. thats why there are charges made for you providing a resistance to that flow with your load. Naturally there are losses in transmission and you of course pay for any inefficiencies in your equipment.

sometimes the old saws are the best.

i guess if we mixed this with the water analogy we would get rust.

Current flows in a complete circuit, so regardless of which direction it is flowing, it leaves the generator in one or more lines, and returns in others. So yes, the current goes out and back. However, the current that returns is at a low potential, and can not do any more work. The generator must lift that current to a higher potential before it can go out again.

Current is NOT power. If the current does any work or produces any heat out on the circuit, then that is power that the generator produces, which does not return. It is gone, and your electric meter accumulates it over time (energy), and you pay for it.

Ben Miller

It is really all about extracting energy from somewhere and delivering it in a usable form somewhere else.

Don't get lost in the terms used (easy to do). Take a gasoline engine and hook it to a generator. The gasoline burns, which converts chemical energy to heat energy. The heat energy causes gas to expand - that motion has kinetic energy. That motion spins the generator, and the kinetic energy is converted to electrical energy. Thus someone could say the generator "pulls" energy from the rotation of the engine crankshaft, which in turn "pulls" energy from the expanding gas, which in turn "pulls" energy from the heat produced by the combustion of the gasoline, which in turn had the energy stored in it chemically.

Ed

In both AC and DC current, there is nothing that goes from the generator to the load and back to the generator !!!! The electric current consists of "motion of electrons". . . . The voltage created in a generator wants to "push" electrons out. . . . and any one electron (in the conductor) goes only from one atom to the next atom, and that motion has the speed of light!!!!. Once an atom receive an extra electron, that atom will force one of its own electron to travel to the next atom, and so on. . . . like if you have a along train stopped on its track and you give a jolt to the first wagon, you find that the last wagon will jump.