How is AC electricity made?? I may need BruceB for this one.

[JustJason]

Okay,
I have taken many courses in electricity from high school to college level, and there is always 1 question I can never find an answer for that satisfies me.
How is AC electricity made?

First let me say that I am comfortabe with DC electricity. I understand chemical reactions. I know about annodes and cathodes. I get free electrons.

However, E is still E, wether it is AC or DC (unless I am missing something) and E is electromotive force. Or, more simply, the flow of electrons.

In DC electricity, I see how electrons are produced. I have done the chemical reaction formulas in school. It all makes sense to me, and I have no quesitons about it.

But what about AC electricity? I know to generate electricity that you need a coil of wire around an iron core, and a magnet to sweep that core in close proximity to it.
But how does it actually all work? Is E in AC still the flow of electrons? I am assuming it is. Where to the electrons come from? Matter can not be created or destroyed, only changed, so what matter is it, and how to the electons form?
It is not chemical, so what specifically happens when a magnet sweeps that iron core? Can anybody here break down what the process is for me?

If anybody answers this... be warned.. I am going to ask about microwave next

 

[rbh]

Re: How is AC electricity made?? I may need BruceB for this one.

google tesla first, he was the man!!!

 

[PiratePast40]

Re: How is AC electricity made?? I may need BruceB for this one.

Once you figure out the issue of repeatedly breaking a magnetic field, wrap your head around the immense power of 1100 megawatts of power generated by a nuclear reactor. Convert the energy to steam, transport the steam to a turbine and spin a generator rotor. Then put all that energy onto cables on the grid! It's really pretty awesome.

Then imagine a nuclear core about the size of a large trash can pushing a 300 foot submarine at 30+ knots UNDERWATER. Incredible amounts of energy with multiple state and phase conversions.

We've learned to do some amazing things with energy.

 

[rbh]

Re: How is AC electricity made?? I may need BruceB for this one.

Once you figure out the issue of repeatedly breaking a magnetic field, wrap your head around the immense power of 1100 megawatts of power generated by a nuclear reactor. Convert the energy to steam, transport the steam to a turbine and spin a generator rotor. Then put all that energy onto cables on the grid! It's really pretty awesome.

Then imagine a nuclear core about the size of a large trash can pushing a 300 foot submarine at 30+ knots UNDERWATER. Incredible amounts of energy with multiple state and phase conversions.

We've learned to do some amazing things with energy.

Now your just "confusing" him---

and me

 

[mscher]

Re: How is AC electricity made?? I may need BruceB for this one.

If I remember USAF Tech school right, electrons are not made, only moved. Chemically in the case of battery DC, and by EMF, when using magnetic generation.

Farady's law can explain things - or make things even much more confusing.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/farlaw.html#c1

Microwaves are easy.

 

[jlinder]

Re: How is AC electricity made?? I may need BruceB for this one.

3 elements to a generator or motor: conductor for the electricity to flow through, magnetic field, and movement (or force to move). If you have 2 it will give you the other one.

Take a magnetic field and move a conductor through it. This will cause electrons to flow (electricity) and give you a generator. To get enough power to do anything you need to wrap the wire in a coil with a lot of wraps so there are a lot of conductors going through the magnetic field.

Do this and make it move through the field by rotating it and you have a generator. Or you can supply power (voltage) to the wire and it will cause it to try to rotate and you have a motor. Same thing really you just apply mechanical force (spin it) in one and electrical energy (voltage) in the other.

You get AC when the coils effectively reverse direction through the magnetic field. This happens every time the coils do a rotation. First the coil is going past the north pole of the field, then going through the south pole. The direction is the same but the magnetic field is different because it is going past a different pole every 1/2 rotation.

Spin the generator at 3600 RPM (60 rev. per second) and you get 60 Hz.

For AC you just attach the ends of the wire coil to 2 rings on the shaft and that connects to the outside world by a conductor that rides on it (brushes).

For DC you have one ring but it is split in half. One wire connects to one have the other to the other half. That way while the magnetic field the coil is exposed to reverses every half rotation, so does the wire connection, so you get DC.

Hope this helped.

 

[rodbolt]

Re: How is AC electricity made?? I may need BruceB for this one.

generators produce DC, Altenators produce AC.
generators have an armeture, altenators have a rotor.
two basic ways to produce AC current.
one is to rotate a magnetic field (rotor) around a stationay set of coils(stator).
two is to rotate a set of coils(rotor) around a magnetic field(stator).
most outboards use the first method.
most cars and power plants use the second.
electromotive force(E) is simply a measure of electrical pressure typically specifed in Volts.
has NOTHING to do with current.
current is the measure of electron flow past a given point and is measured in amperage.
which is why secondary side of the ignition system can generate 30,000+ volts and not kill you when you get bit.
the voltage is very high but the current is very low.
on most beltdriven car altenators the stator is a stationary set of coils.
pass an electrical current throgh the coils and it sets up a magnetic field.
rotate another set of coils through this magnetic field and you get AC current.
years ago most cars had a generator, it was simple but very ineffecient.
only produced 1/2 the current an altenator does at the same rotational speed.
worked well with the tecnology in the 40's to the 70's.
then the electrical demends on most cars became more than the generator was worth and the advent of modern electronics made alternators more effective and less costly than generators.

 

[JustJason]

Re: How is AC electricity made?? I may need BruceB for this one.

Rodbolt and Jlinder,
I understand all that, I guess more specifically I should have asked... where do the electrons come from?

 

[spdracr39]

Re: How is AC electricity made?? I may need BruceB for this one.

Very basically
DC = direct current meaning the electrons actually flow from point a to point b
AC = alternating current meaning the forward and reverse polarity from the magnetic field in the generator vibrates the electrons and the vibration is current. The electrons don't actually travel they just vibrate back and forth.

 

[dwco5051]

Re: How is AC electricity made?? I may need BruceB for this one.

Rodbolt and Jlinder,
I understand all that, I guess more specifically I should have asked... where do the electrons come from?

The electrons are not created. The electrons are present in the atoms of the conductors. When excited by the emf of the generator they move from the valence shell of one atom to the next and are forced to the next atom and so on. That is why a complete circuit is needed as they eventually return through the conductors to the generator. The actual flow of electrons is very complicated, especially in AC circuits but this is a simple explanation.

 

[jlinder]

Re: How is AC electricity made?? I may need BruceB for this one.

rodbolt -

The move from DC generators to AC alternators had more to do with the availability of reliable solid state diodes to convert the AC back to DC than anything else.

Generators have a problem in that the voltage is proportional to the speed of the generator, which is dependent on the speed of the engine. At idle the generator does not create enough voltage to put any charge into the battery. That is why the headlights on the older cars would dim somewhat when idling.

Alternators on the other hand can be designed to have the voltage peak exceed the voltage of the battery. Peak - not the average. This means that at idle the alternator still puts out some current to the battery.

If you had an engine that ran at a constant RPM you would be better off with a generator.

A great example of this is a helicopter. (I used to do some flying in a Bell Jet Ranger). Helicopters run with a constant RPM for the rotor (at least this one did). They use a generator instead of an alternator.

Interesting side note is the same generator serves as the starter motor. They use it to get the jet engine up to speed (at least enough to get it to light and run), turn it off for 60 seconds to let it cool down (takes a long time to spin the jet up to speed), then use it as a generator to charge the electrical system.

 

[dolluper]

Re: How is AC electricity made?? I may need BruceB for this one.

I find the interesting part is AC is made then transmitted at high volts ....alot lost on the way because of the bouncing around of the electrons .....then in most cases going through a step down transformer ......just a big coil like auto one, primary + secondary ...done by the number of turns...[or wrap around}.....then to make to finally an electric toothbrush using a coil...transformer ...again to charge the tooth brushes battery and calling THE COIL an induction charger ....fancy name for just a coil

 

[dwco5051]

Re: How is AC electricity made?? I may need BruceB for this one.

I find the interesting part is AC is made then transmitted at high volts ....alot lost on the way because of the bouncing around of the electrons .....then in most cases going through a step down transformer ......just a big coil like auto one, primary + secondary ...done by the number of turns...[or wrap around}.....then to make to finally an electric toothbrush using a coil...transformer ...again to charge the tooth brushes battery and calling THE COIL an induction charger ....fancy name for just a coil

That is the reason Tesla's idea to transmit power by AC beat out Edison's DC system. The fact is that AC power can be stepped up to transmit it long distances then be stepped back down at point of use with a whole lot less energy being wasted.

 

[dolluper]

Re: How is AC electricity made?? I may need BruceB for this one.

Step up transformers and step down transformers AKA just coils same as most appliances stepping up or down on application needs.....a coil.. so many turns of wire on the primary ,iron bar .empty space ,and so many turns on the secondary so easy to accomplish

 

[rbh]

Re: How is AC electricity made?? I may need BruceB for this one.

just to add and confuse.


http://en.wikipedia.org/wiki/Corona_discharge

 

[dolluper]

Re: How is AC electricity made?? I may need BruceB for this one.

Carp I better go and check on my Nitrogen Laser

 

[dvandsm64]

Re: How is AC electricity made?? I may need BruceB for this one.

i am an electrician. i don't know about these other answers. we always just say electricity is magic.

 

[rbh]

Re: How is AC electricity made?? I may need BruceB for this one.

Carp I better go and check on my Nitrogen Laser

HAHAHA.
I still remember "some" of the stuff we took when it came to transmission and distrabution theory of power during lineman school, now I remember why I went telecom.
(only to come up against more and more different equations, IE wheatstone bridge SP)

 

[jlinder]

Re: How is AC electricity made?? I may need BruceB for this one.

AC is preferred when you want an easy way to step the voltage up and down. This is great when you want to transmit it at high voltage to reduce current and losses then step it down to less dangerous levels for distribution into the home.

However, when you are talking about moving huge amounts of power long distance they use DC. The main power grids in the US and other countries use DC to move the power long distances then convert back to AC for local distribution.
http://en.wikipedia.org/wiki/Electric_power_transmission

 

[jonesg]

Re: How is AC electricity made?? I may need BruceB for this one.

"I guess more specifically I should have asked... where do the electrons come from? "

They aren't free energy created, they are just converted from the thermal energy from the engine through mechanical means applied to the alternator.

If you look at Faradays first crude elec motor he noticed how putting v into it(through the recently invented battery by the Italian Volta) caused it to spin.

He then noticed if he spun the motor armature by mechanical means he could produce voltage.

It was merely converting the physical spin energy to v.

Heres Faraday's "motor". This is as simple as it can get besides a compass.
When he demonstrated it to the prime minister, seeking funding, the PM said its interesting but what use is it?
Faraday replied "you can tax it". He got his money.
http://www.youtube.com/watch?v=R-Ma6iKLd7g&feature=related