I may not fit your criteria for posting

[pratto]

I am a retired Civil engineer, but would like to make a post in the Electrical Engineers forum.

My experience in this field is limited (in florida they stopped letting us do load calculations long ago). Just doing a little reading about AC power, and repairing my own house wiring.

But in trying to explain away the boogyman of AC in the home to a friend, I realized that maybe I should look at some YouTube videos to clear up some gray areas. But what a collection of garbage did I find. They say any moron can post an instructional youtube video, and they sure have.

This inspired me to make one of my own, about what AC power means to most people. And before I prove that I am just as stupid as the other posters, I thought I had better write down my understanding of AC for the common man.

Once I did, I thought hmmm... I'd better bounce this off some people who actually know what they are doing, i.e. Power Engineers.

May I post my understanding here and ask for comments ?

 

[Skogsgurra]

I wouldn't mind. There used to be a very strict policy: Engineers, professional issues only, stick to your field of expertise, don't promote yourself or your business and, certainly, no student posting.

This policy has been debated thoroughly over the years and it seems that the general opinion is that as long as there's not an obvious abuse, questions like yours are accepted. Especially when someone asks as humbly as you do.

There's always a risk that someone will red-flag your post. But I don't think that will happen. And if it happens - it doesn't necessarily mean that your post willl be removed. That is something that the Powers decide. And there are ways that we can inform those Powers what we think about their actions.

So, do post! It is usually interesting to read about something you think that you master fairly well when someone intelligent writes about it the way he/she sees it.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[jraef]

Well, you have apparently already cleared one major hurdle, skogsgura can be tough. So if he's ok, I doubt anyone else will be worse...

Fire away!


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[Skogsgurra]

Thanks, Jeff. But remember - there's always Kenat...

What happened to your memories of salami, BTW?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[waross]

Gone to be with the fingers and electrons??? grin

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[sibeen]

As long as you mention beer, and the head on the beer, I imagine skogsgura will be happy.

 

[Skogsgurra]

Dear Pratto.

Just ask your question. My "friends" are only joking. You will get used to them - as I am - eventually.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[pratto]

Hello =

Thanks for the friendly reception.
Since I posted my request I re-read my take on simplified AC and have gotten embarrassed about my approach and simplistic analogies. It is also pretty long winded, and I have decided to try to trim it down so as to not try your patience. I know from my own experience that listening to someone who is ignorant is hard enough, but when they go on and on it can send me over the edge.

Here is a point that I haven't seen anyone explain. To show my friend the most fundamental concept of electro-magnetism, I made a coil of wire and connected a uA panel meter (D'Arnseval I think) to its ends. Then I passed a strong bar magnet by the coil. Sure enough my little meter showed current flow. Positive if I moved the magnet one way, and pegging (trying to move below zero) when I moved it the other way. A nice visual aid. I intended to show that the more lines of magnetic flux that were cut, and the more coils of wires there were, the stronger the current would be. A rotating coil would cut more lines of flux in one orientation than in another. Therefor the current would increase and decrease.

Great. Having got my experiment ready to show him, I contemplated on his reaction. He has a habit of asking me questions about AC that I haven't considered and can't answer. I can imagine him saying, "ok, I can physically see that the amount of current does go up and down (greater and lesser), but where does voltage come in"?

In none of the books or articles that I've read, nor in any of the videos I've seen, does anybody get past the current. Maybe it is so obvious to everybody that it doesn't need to be expounded on, but not to me.

What is the relation between the amount of current and the voltage ? I know that a small voltage can deliver a large current, and vice versa. My wall outlet at 120v rms can deliver 1 amp, but it can also deliver 10 amps, still at 120v. Does the physical size of the generator determine the voltage ? Is it a function of the wire size ?

As you can see, I'm not ready to be an explainer yet.

 

[waross]

Back to basics. If you had reviewed your theory, you would have seen that the voltage induced depends on the strength of the magnetic field, and the number of lines of force cut per unit of time. The current depends on the induced voltage and the impedance of the circuit, in your case both the impedance of the coil and the impedance of the meter.
As a suggestion, review your old high school science text books.

Bill
--------------------
"Why not the best?"
Jimmy Carter