Help with electricity

[redtail]

You had it correct the first time. ampere per second would be a rate of change of current flow. A coulomb is a quantity of charge and 1 ampere is a rate at which charge flows.



At the very least he had a nice cage named for him.



You knew one of my EE professors? One of his famous quotes was about Uncle Kirchoff's plumbing law. "The sum of the currents into a paper bag is zero".

Yeah I've been out of school too long.
Thanks

 

[Henning]

You had it correct the first time. ampere per second would be a rate of change of current flow. A coulomb is a quantity of charge and 1 ampere is a rate at which charge flows.



At the very least he had a nice cage named for him.



You knew one of my EE professors? One of his famous quotes was about Uncle Kirchoff's plumbing law. "The sum of the currents into a paper bag is zero".

Here we go, you're the man to ask, can you tell me how far the electrons move in their pulse cycle?

 

[redtail]

So based on my new sig, I'll make the following statement to clarify my position as an electrician and NOT an engineer.

What makes the most sense to me in my line of work is... Current=Electron Flow, not Hole flow. Both concepts can be as equally valid as they are flawed. However, an electron flowing from one atom to the next and leaving a hole in it's wake..... Just makes more sense (to me) than the opposite!

see my sig

 

[spiderweb]

Really? What have you read? Has anyone managed to say anything besides what concludes to "Wow, cool, WTF?" yet? It's interesting though, verry interesting, but not funny.

It is really, really cool!

 

[alfadog]

I wanted basic, and got it.

Meanwhile--for fun, mind you--I have been reading up on quantum entanglement. But that's for another reason; not for helping me understand what's going on under the cowling!

quantum entanglement? Is that like a quickie with a total stranger?

 

[Ghery]

Here we go, you're the man to ask, can you tell me how far the electrons move in their pulse cycle?

So short a distance you wouldn't care. I'd have to dig around, but it isn't far.

 

[Henning]

quantum entanglement? Is that like a quickie with a total stranger?

It's what indicates there is a common 'carrier wave' to the information that is ordered into our universe.

 

[Henning]

So short a distance you wouldn't care. I'd have to dig around, but it isn't far.

So nowhere near light speed or through a tightly spiraling wrapping path around the surface of the strand?

 

[spiderweb]

quantum entanglement? Is that like a quickie with a total stranger?

It's like a quickie at the subatomic level with any other subatomic entity, anywhere in the galaxy.

 

[Hiperbiper]

what is volts agin?

 

[Henning]

what is volts agin?

Head pressure of God's pee.

 

[Ghery]

So nowhere near light speed or through a tightly spiraling wrapping path around the surface of the strand?

Nowhere near for an individual electron. The effect goes down the wire at the speed of light in that medium, but individual electrons don't go very far at all.

 

[DouglasBader]

Negatory. A DC generator uses a commutator to reverse the current in the windings each half turn so it outputs DC. An alternator makes the correction with a rectifier after the electricity is generated. Older vehicles used to use DC generators but now almost univerally use alternators. However, you are not incorrect in calling your AC generators, "generators", and not "alternators", as the below from Wikipedia indicates:

Negatory.

A DC Generator uses rectification, generally in the form of diodes for light aircraft, to reduce the natural AC output to DC.

An alternator doesn't need to do this: all generators output AC.

Older vehicles use DC generators: these are AC generators which use diodes to rectify, or filter the output to provide a DC output. All generators are AC.

Modern vehicles use alternators. These are AC generators, just as the older vehicles are AC generators.

Your thinking that generators are DC and alternators are AC is wrong. All generators make or generate AC electricity. All alternators are generators. All alternators and all generators make AC electricity. What's delivered to the customer system varies according to the customer needs.

For your purposes, the difference that you need to know is that alternators are a little more complex, don't need excitation, don't need the field to be flashed, and most importantly for you, whereas a generator doesn't normally have a stable output at low RPM engine power settings, the alternator does.

In more complex aircraft, we often use starter-generators to save weight; one motor that is either functioning as a generator at higher speeds, or functioning as a starter at lower speeds. We also use AC generators in many cases.

 

[denverpilot]

Head pressure of God's pee.

Actually not a bad analogy for lightning.

The sheer numbers of electrons involved in a single lightning strike is mind-boggling.

Designing a lightning protection system in the 2nd highest number of lightning strikes State behind Florida which is #1, for radio towers ... Is interesting.

More interesting is seeing that usually, it works. Direct hits usually result in physical damage to antennas but done right, the radio on the other end of the hardline usually... usually survives. DC grounded antennas like folded dipoles fair well. Fiberglass whips with a small conductor inside, explode. You can usually scoop up the pieces of a 20' tall antenna into a small kitchen trash bag. Arc "weld" holes are common and antenna sections on really big antenna arrays get welded together.

The trick is not to attempt to keep the lightning out of the building, but to bind every darn thing in sight together with very low resistance conductors (big copper "halos" and wide copper straps) so the voltage potential rises and falls equally and gives the strike time (not much time!) to drain off via multiple bonded earth grounds before it jumps a gap and fries something more delicate. Gas-discharge devices on antenna coax/hardline all bonded to a copper entrance panel at ONE point and a nice fat wide copper strap straight down to the around-building buried halo of copper with multiple driven ground rods.

All that copper is expensive at today's prices.

Give it somewhere to go that "looks" like a better ground path at extremely high voltages and it will go that way.

Phone lines suck. They bring the most destruction indoors followed by improperly protected AC power. I've seen the shrapnel of all the plugs of a power strip embedded into every nook and cranny of a properly grounded and protected rack cabinet. That was kinda cool, other than every piece of equipment plugged into the strip going off-air simultaneously. Poof!

 

[alfadog]

Negatory.

A DC Generator uses rectification, generally in the form of diodes for light aircraft, to reduce the natural AC output to DC.

An alternator doesn't need to do this: all generators output AC.

Older vehicles use DC generators: these are AC generators which use diodes to rectify, or filter the output to provide a DC output. All generators are AC.

Modern vehicles use alternators. These are AC generators, just as the older vehicles are AC generators.

Your thinking that generators are DC and alternators are AC is wrong. All generators make or generate AC electricity. All alternators are generators. All alternators and all generators make AC electricity. What's delivered to the customer system varies according to the customer needs.

For your purposes, the difference that you need to know is that alternators are a little more complex, don't need excitation, don't need the field to be flashed, and most importantly for you, whereas a generator doesn't normally have a stable output at low RPM engine power settings, the alternator does.

In more complex aircraft, we often use starter-generators to save weight; one motor that is either functioning as a generator at higher speeds, or functioning as a starter at lower speeds. We also use AC generators in many cases.

OK. You are both correct and incorrect. Yes, an armature rotating in a magnetic field that has a constant N/S will produce an alternating induced current. However, you are leaving out the commutator. DC generators, also called dynamos, do not use rectifiers (diodes).

You are misinterpreting me, though, with this: "Your thinking that generators are DC and alternators are AC is wrong." Where did I say that? I specifically provided a quote showing when the term "alternator" is used and when the term "generator" is used for an AC generator. So the term "generator" can apply to either an AC or DC generator.

So the difference is not whether an AC generator is self-exciting while a DC generator is not or some-such but whether it uses a commutator (dynamo) or rectifier (alternator). Assuming both are designed to produce direct current. Both are called "generators" generally.

 

[redtail]

Do you know what a commutator is? DC generators do not use rectifiers (diodes). They output DC because the field in the windings is being reversed each half turn. Since it is the field that creates the current that is being reversed and not the current itself we rightly say it generates DC.

You are misinterpreting me with this: "Your thinking that generators are DC and alternators are AC is wrong." Where did I say that? I specifically provided a quote showing when the term "alternator" is used and when the term "generator" is used for an AC generator. So the term "generator" can apply to either an AC or DC generator.

That's basically what I was saying also. The commutator is just a rotating switch, a split ring that takes the AC and transforms it into a pulsating DC. It takes the negative half of the sine wave and reverses it. The external circuit sees detects current flow in only one direction (unlike the alternator). You can smooth out the pulses by adding more than one coil and using rectifiers filters. But as someone else stated, all DC generators actually produce AC inside the windings. Unless you're talking about Farraday's disk

So in that respect, DC generators are not like Batteries.

 

[alfadog]

That's basically what I was saying also. The commutator is just a rotating switch, a split ring that takes the AC and transforms it into a pulsating DC. It takes the negative half of the sine wave and reverses it. The external circuit sees detects current flow in only one direction (unlike the alternator). You can smooth out the pulses by adding more than one coil and using rectifiers. But as someone else stated, all DC generators actually produce AC inside the windings. Unless you're talking about Farraday's disk

So in that respect, DC generators are not like Batteries.

Yes, I edited the post since you replied. I stand corrected and it makes sense with a little thought that a rotating armature will produce an alternating current in a fixed magnetic field. The fellow that corrected me also needs to update his knowledge, however, as his understanding was incomplete also.

I saw Farraday's disk but do not understand how it would produce DC. I did not look into it, however. Maybe I will now.

 

[redtail]

Yes, I edited the post since you replied. I stand corrected and it makes sense with a little thought that a rotating armature will produce an alternating current in a fixed magnetic field. The fellow that corrected me also needs to update his knowledge, however, as his understanding was incomplete also.

I saw Farraday's disk but do not understand how it would produce DC. I did not look into it, however. Maybe I will now.

Correction, I should have said "filters", capacitors, not rectifiers. A rectifier basically does the same thing that the commutator does (takes a reversing polarity signal (AC) and channels it in one direction, DC). Keep in mind, I'm trying to stick to basics.

 

[alfadog]

Correction, I should have said "filters", capacitors, not rectifiers. A rectifier basically does the same thing that the commutator does (takes a reversing polarity signal and channels it in one direction, DC). Keep in mind, I'm trying to stick to basics.

Yes, I imagine that a commutator and a simple diode bridge (full-wave rectifier) will produce similar pulsed DC. And don't dumb anything down on my behalf.

 

[redtail]

And don't dumb anything down on my behalf.

No, I meant keep it simple for my own mind. I haven't studied this stuff much since I graduated many years ago. On my job, I deal more with the practical application of it as opposed to what's going on underneath.

Wish I had stayed in DeVry though and got my engineering degree. I dropped out 26 years ago to go work on runway lighting and various other industrial electrical applications.

 

[alfadog]

No, I meant keep it simple for my own mind. I haven't studied this stuff much since I graduated many years ago. On my job, I deal more with the practical application of it as opposed to what's going on underneath.

Wish I had stayed in DeVry though and got my engineering degree. I dropped out 26 years ago to go work on runway lighting and various other industrial electrical applications.

Never too late to go back. I got my BSCE at the age of 44. Though I enjoyed my job more as a heavy equipment operator than I do as an environmental engineer. It is a lot more fun pushing big piles of dirt around than pushing pixels (though I mainly ran a trackhoe and did more digging than pushing). That is why I am retiring soon.

 

[redtail]

Never too late to go back. I got my BSCE at the age of 44. Though I enjoyed my job more as a heavy equipment operator than I do as an enviromental engineer. It is a lot more fun pushing big piles of dirt around than pushing pixels (though I mainly ran a trackhoe and did more digging than pushing). That is why I am retiring soon.

Yeah I hear ya. That's basically what happened to me. I started working with electricians at KEWR & KLGA. I was in a high school work/study program. I really enjoyed the hands on work installing and repairing runway/taxiway lighting, contant current transformers (used in runway/taxiway lighting systems,etc), three phase motors, etc. and of course....being around aircraft everyday.

Graduated high school, worked with an electrical contractor doing residential (which I wasn't really too crazy about). Quit the contractor, started attending DeVry and loved it! Their electronics courses were great! Man I loved that stuff.

However, my company sent me an invitation to come on board and return to the airport as an electrician. The joy that I got working there in high school made it hard to resist the offer. Tough choice to drop out of DeVry though. Kept telling myself that I'd go back and continue while working but it just never happened.

Got married, had a couple of kids and just never made time to go back to school. Oh well, I can't complain. I have a very rewarding career and make a decent living (26 years). Hey, like you said...it's never too late. Maybe I'll go back afterall

 

[Graueradler]

The commutator is just a rotating switch, a split ring that takes the AC and transforms it into a pulsating DC. It takes the negative half of the sine wave and reverses it. The external circuit sees detects current flow in only one direction (unlike the alternator). You can smooth out the pulses by adding more than one coil and using rectifiers filters. But as someone else stated, all DC generators actually produce AC inside the windings. Unless you're talking about Farraday's disk

So in that respect, DC generators are not like Batteries.

Being picky but the "generator" windings actually produce an alternating voltage, not an alternating current. Only the winding connected to the brushes through the commutator at the moment produces any current. The other windings are open ended and produce no current. Since only the winding that is near peak voltage in the desired polarity is connected to the brushes, the current is always in the same direction (DC). Since the winding voltage varies slightly as it changes angle in the magnetic field while it is connected to the brushes and since there is a voltage step as the commutator segments switch under the brushes, the output voltage and current has a ripple. I think of "pulsed" as going to zero between pulses. Since the brushes overlap commutator segments, the voltage does not drop to zero between segments (not pulsed).

 

[Henning]

Nowhere near for an individual electron. The effect goes down the wire at the speed of light in that medium, but individual electrons don't go very far at all.

So it's like the horizontal stack of suspended metal balls that knock back and forth? The stack barely shifts but transmits it's energy quickly?

 

[redtail]

Being picky but the "generator" windings actually produce an alternating voltage, not an alternating current. Only the winding connected to the brushes through the commutator at the moment produces any current. The other windings are open ended and produce no current. Since only the winding that is near peak voltage in the desired polarity is connected to the brushes, the current is always in the same direction (DC). Since the winding voltage varies slightly as it changes angle in the magnetic field while it is connected to the brushes and since there is a voltage step as the commutator segments switch under the brushes, the output voltage and current has a ripple. I think of "pulsed" as going to zero between pulses. Since the brushes overlap commutator segments, the voltage does not drop to zero between segments (not pulsed).

True about the lack of current flow until connected to the external circuit but I thought that was pretty obvious. In keeping with simplicity, I'm sure you'll agree..... They're called Alternating Current (AC) & Direct Current (DC) generators, not Alternating Voltage(AV) nor Direct Voltage(DV) generators.

That's a pretty good description you gave.

Ripple probably is a more accurate description of the waveform but in most text, it's called Pulsating DC.

 

[redtail]

but I agree, it's only an Alternating Voltage until it's doing work. Then it becomes both, Alternating Voltage AND current

 

[redtail]

I guess the other thing to consider is... in it's most basic form, the wave is indeed pulsing. It's passing zero volts (180 degrees) every half cycle. In that respect, it's pulsating DC but you're correct, the actual output will be a ripple (never dropping to zero) because there are multiple windings on the rotor connected to a multi-segmented commutator.

 

[Henning]

I guess the other thing to consider is... in it's most basic form, the wave is indeed pulsing. It's passing zero volts (180 degrees) every half cycle. It that respect, it's pulsating DC but you're correct, the actual output will be a ripple (never dropping to zero) because there are multiple windings on the rotor connected to a multi-segmented commutator.

I thought from his description it was more of a 'synched graduated overlap' rather than pulsed?

 

[Piloto]

So it's like the horizontal stack of suspended metal balls that knock back and forth? The stack barely shifts but transmits it's energy quickly?

Yes it is. The same analogy applies to sound propagation in solids, water and air.

José

 

[Henning]

So the electron doesn't need to flow, it just passes on its charge pressure to the electron in the shell next door and so on. The electrons don't move, but through the pressure of charged energy stacked behind it passes that pressure down the line through repulsion?

 

[Graueradler]

I thought from his description it was more of a 'synched graduated overlap' rather than pulsed?

Right. Look at the physical width of the brushes compared to the gap between segments on the commutator. There is always contact between the brushes and either one winding or two adjacent windings.

Another advantage of the alternator over the generator is brush & commutator wear. The generator rotor carries the output of the device so the brushes are interrupting a fairly high current each time they disconnect from a winding. That is sparking and wear. The alternator uses the rotor for the field so the brushes are carrying the much smaller field current to slip rings instead of commutator segments so even that much smaller current is never interrupted. The output of the alternator is generated in the stator and hardwired through the diodes to the output connector. Since there is less spark generation, the alternator also generates less radio frequency interference that the generator.

 

[Henning]

Right. Look at the physical width of the brushes compared to the gap between segments on the commutator. There is always contact between the brushes and either one winding or two adjacent windings.

Another advantage of the alternator over the generator is brush & commutator wear. The generator rotor carries the output of the device so the brushes are interrupting a fairly high current each time they disconnect from a winding. That is sparking and wear. The alternator uses the rotor for the field so the brushes are carrying the much smaller field current to slip rings instead of commutator segments so even that much smaller current is never interrupted. The output of the alternator is generated in the stator and hardwired through the diodes to the output connector. Since there is less spark generation, the alternator also generates less radio frequency interference that the generator.

My class on generators and alternators was much shorter but I understand DC generators to work as you describe. Having rebuilt many different units, it always seemed kinda obvious to me.

 

[Piloto]

So the electron doesn't need to flow, it just passes on its charge pressure to the electron in the shell next door and so on. The electrons don't move, but through the pressure of charged energy stacked behind it passes that pressure down the line through repulsion?

Good point because the conduction mechanism still not that well known. So it can be either what you have stated above or simply mometum exchange m1v1 = m2v2.

José

 

[Henning]

Good point because the conduction mechanism still not that well known. So it can be either what you have stated above or simply mometum exchange m1v1 = m2v2.

José

It seems like a pressure equation and the mechanism is the increased repulsive force of like charged particles as their proximity is reduced. As you 'squeeze' the atoms together excited with potential, the electrons get closer together and the repulsive force will increase in an exponential fashion. Kinda holds up with higher voltage being exponentially more thermally efficient than lower voltage as well.

 

[redtail]

So the electron doesn't need to flow, it just passes on its charge pressure to the electron in the shell next door and so on. The electrons don't move, but through the pressure of charged energy stacked behind it passes that pressure down the line through repulsion?

I'm glad you posed that as a question and not a fact, because from what I was taught, what you described is emf (electromotive force). Potential difference that causes electrons to flow from atom to atom seeking to balance that difference.

Like water seeking it's level or air flow over an airfoil. High pressure seeking low pressure. Remember wingtip vortices? Does not air "flow" from high pressure to low?

Then again, remember what I said about theories. At one time the theory of only nine planets in our solar system, was taught as fact!

 

[redtail]

"electro-motive" force. A force that causes motion (motive). Motion=flow

 

[Cap'n Jack]

Then again, remember what I said about theories. At one time the theory of only nine planets in our solar system, was taught as fact!

This doesn't take away from your point about theories, but the number of planets stems from how one defines a planet as much as anything else. After all, Pluto didn't go away- we just found stuff that made us rethink what defines a planet.

 

[redtail]

This doesn't take away from your point about theories, but the number of planets stems from how one defines a planet as much as anything else. After all, Pluto didn't go away- we just found stuff that made us rethink what defines a planet.

Absolutely. That's my point. The textbooks will change again as long as we continue to discover differences in what we thought we knew were facts. Some scientist outright reject the new definition of planet. To them, Pluto is still one.

Where we go wrong (IMO) is...oftentimes we quote theories as facts.

There's nothing wrong with studying and formulating ideas, that's how we grow in knowledge, but we should always keep in mind that these ideas may be proven to be flawed.

 

[redtail]

I could define a planet as an object that rotates around a star and has known life forms. Under MY new definition, we only have one planet in the universe...Earth

 

[Cap'n Jack]

I could define a planet as an object that rotates around a star that has known life forms. Under MY new definition, we only have one planet in the universe...Earth

And that works too.