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PostPosted: Thu Oct 13, 2005 6:36 pm 
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88 Coupe wrote:
Hi andrewk, All,

Quote:
........ on older cars and most farm tractors, current flow goes neg to pos ......... When they changed from generators to alternators, the electrical system changed to negative ground ........

Change to neg ground was made with the change from 6 to 12Volts.

Don't know about farm tractors, but Ford was the last to change. '55 was 6v pos, '56 was 12v neg.

Alternators did not appear until the early 60s.

Regards, Norm


yes, I knew that!! :blush: I guess I need a smack in the ol' forehead!! :lol:



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PostPosted: Thu Oct 13, 2005 9:10 pm 
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delta im not sure if this is right or not but the visual part of the lighting coming from the clouds to ground i think it starts up there do to the atmospheric pressure difference. might cause more of a disturbance up there then it does close to the ground. i have no clue if what i said is true or not but it seems logical....I think -Intimidator68


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PostPosted: Sat Oct 15, 2005 12:20 am 
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I talked to my instructor today who has worked on electronics in vehicles for over 30 years. we basically talked about why they switched from positive ground to negative ground. this is basically what he said. the switching wasnt really to make electrics more efficient since there was very little increase in efficency when they did change. he said the major reason they did so was to help corrosion. electrons have a negative charge. and pretty much all chassis have iron or an alloy containing iron. he gave me this equation Fe+02 yields Fe202. during that process which is actually rust, 2 electrons are released when there was positive ground, opposites attracted, there fore rust and corrosion was more prone to vehicles. when switching to negative ground, they hoped it would help repel the electrons since they both would be negative charge. it did help efficenciany a little bit. but he says it wasnt the primary reason they switched. just a little info i thought i would share. -Intimidator68


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PostPosted: Sat Oct 15, 2005 8:51 am 
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Hi Intimidator68, All,

Thanks, it's good to know the facts, after all these years.

Regards, Norm



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PostPosted: Mon Oct 17, 2005 11:37 pm 
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Hi all,

I had this in my Metorology class today. This should help with the lightning debate.

Suppose a big old positively charged up cloud passes overhead. It
attracts electrons from the nearby conducting ground, and they pile
up directly beneath it. They strain to reach the cloud, running up
things like our salty bodies to get closer to the positive charge.
However, they cannot easily jump over to the cloud with all that
insulating air in the way and the field grows faster than the cloud is
neutralized. Eventually the field strength is enough that the air right
above a high point starts to ionize, and BAM - current flows, which
heats the air, which knocks off electrons, which makes more
current flow, which further heats the air, reaching ever higher to the
cloud. In an instant, a lot of charge flows from the ground to the
cloud, which becomes neutralized. The air, a human body, or
anything else granting passage to the huge blast of hot current
sizzles gently in its passing, dead, exploded, burnt. Air rushes back
into the resulting vacuum, creating the roll of thunder.



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PostPosted: Tue Oct 18, 2005 1:21 am 
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hope im never in the way of one of those *knock on wood* -Intimidator68


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PostPosted: Tue Feb 19, 2013 12:34 am 
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Yay Science!!!

Class is in session!


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PostPosted: Thu Nov 21, 2013 5:43 am 
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andrewk wrote:
Brando and all,
I have noticed alot of electrical problems lately, and some unintentional misinformation on electrical repairs and theory. So I thought I would post some stuff on electricity for us all to use. Maybe if you like this, it could become a "sticky" Ill make seperate posts on this thread so it is all located in one place.


To start with, all matter is composed of atoms, which are composed of some basic particles of electric charges. The smallest and lightest are called electrons and are referred to as negative charges. The positive particle is known as the proton. As far as is known, all matter is made up of these particles. Some of the characteristics are: like charges repel each other and unlike charges attract. This is similar to magnets, where like poles repel each other and unlike poles attract. A small experiment you could perform to see this would be to take a metal rod and attach 2 leaves of tin foil to one end and hang it in a glass jar. If you would take a glass or plastic rod and rub it with some fur to charge it up, then touch it to the metal rod, the 2 foil leaves will spread apart. This is due to the fact that that the static charge built up on the rod charges both leaves of the foil and they will physically move apart.

Atoms are composed of a nucleus containing protons that are 1840 times heavier than electrons. Around the nucleus are an equal number of electrons flying around the nucleus like planets orbit the sun in our
solar kits system. How these electrons are arranged determines the stability of the atom. The electrons are in different orbits, but the electrons in the outermost orbit are the ones that we will be observing. For example the hydrogen atom has 1 proton and 1 electron spinning around it making it the lightest atom. Typically the first ring is stable with 2 electrons. The pull on the electron by the proton is offset by the centrifugal force of the electron flying around the proton keeping it in orbit. Since it has one electron and 1 proton, its atomic weight is 1 and the elements go to uranium having an atomic weight of 92 with 92 protons and 92 electrons. Typically the electrons in the outer ring needs to number eight for stability.

Lets look at a couple of atoms that are common in the electrical world. The carbon atom has 6 protons in its nucleus, 2 electrons in the first ring and 4 in the second. The copper atom has 29 protons and 2 electrons in the first ring, 8 in the second, 18 in the third and 1 in the forth. Atoms that do not have 8 electrons in the outside orbit are not stable electrically. The farther from 8, the less stable. In the above examples the outer orbit of copper having 1 electron is less stable than the carbon atom with 4 electrons in the outer orbit. This is a very complex subject and I have picked a couple of atoms and just tried to illustrate what basically happens. If you desire any more information on this subject, get a good Physics book and it will explain it a lot better than I can in this small space. Keep in mind that the sketch of atoms, below, appears like the orbits are all on the same flat plane. In reality electrons are like tennis balls and their orbits, which look like wire grids, make up the "shell" of the atom. As another example, think of our solar system, and picture the sun as the nucleus of the atom and the planets as the electrons.

Image
Now we will look at why these things are significant. If you take a copper wire made of "a gazillion" atoms and put a positive charge at one end this charge will attract one of the unstable electrons from the outer orbit of one of the atoms. This will leave this atom with one more protonthan electron, so it will be unbalanced by 1 positive charge. T his atom will attract an electron from the outer ring of an adjacent atom. The missing electron gets replaced by one from the outer orbit of an adjacent atom. This activity continues from atom to atom creating an electric current. The more positive the charge at the end of the wire the more electrons are moved. The carbon atom with 4 electrons in its outer ring or valence is more stable than copper with only 1 electron. If the same positive charge is applied to a carbon rod, since it is more stable fewer electrons will be attracted and the flow of electrons will be significantly less. Therefore copper is a much better "CONDUCTOR" of electricity than carbon. Also the thicker the material the more atoms there to give and receiver electrons, so the greater capacity for electron flow.

An atom that has 8 electrons in its outer ring or valence is stable and the electrons will not leave the orbit in response to a positive charge. This material is called an "INSULATOR". (These materials are also called DIELECTRICS.)

When an electric current is flowing in a conductor another curious thing occurs. The flow of electrons creates a magnetic field around the conductor. Conversely another unique thing happens. If you move a magnetic field across a conductor it causes the electrons to flow the same as applying a charge at the end of the conductor does. What is happening is we are converting mechanical energy to electrical energy. As we get into this deeper we will see how these factors are adapted to motors, generators, solenoids, transformers, ignition coils, voltage regulators etc.

THERE IS ONE VERY CONFUSING ITEM: ELECTRON FLOW IS FROM NEGATIVE TO POSITIVE. IN GENERAL PRACTICE CURRENT FLOW IS SAID TO BE FROM POSITIVE TO NEGATIVE. In normal discussion people usually think of current flowing from positive to negative, and as we go forward, we will probably use that terminology. I think it is important that we have an understanding about atomically what an electric current is.

There is one other law of physics we must remember and that is: "Energy can neither be created or destroyed, but may be transformed." So as we journey forward, remember that electron flow may be transformed to mechanical energy, heat, etc. and these items may be transformed into electron flow
.

Awesome electrical stuff..You have shared detailed information about electricity which is very exciting.. I would love to use the information in positive manner.


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