There are at least two parts to what you're asking about: knowing how to hook stuff up, and getting the wires from here to there.

There is plenty of info available about networking and cabling, but no book can teach one how to run wiring like experience can.

That's why licensed specialty trades (electrical, plumbing,HVAC, etc.) require both schooling and on-the-job experience.

I wasn't trying to be a wise(beep) when I answered the way I did, just direct and to the point. I can teach one more in a week than you can learn from a book in a year.

Because I've been into electronics since I was 5, I've known electrical theory as well as any master I've worked under, but I had to learn the nuts'n'bolt the hard way.

Larry
www.fineelectricco.com

I understand Larry runs his own daily field trip of future installers, a bus full of five-year-olds, swinging out to the suburbs after kindergarten, to get some solid construction background skills. Calls 'em "the Tiny Watchers."

LOL! Ernie, you're so too much! That's a riot!

Seriously, whenenver a kid (of any age) is interested in what I'm doing, I'm happy to take the time to explain the why's and wherefor's of my work.

Just this past week, I explained in two minutes the nature of electricity (in terms of valence shells and free electrons) to a customer, and she got it.

Larry
www.fineelectricco.com

Could you record that 2-minute explanation as an mp3 and post a link here? ;))

The science of AC current still eludes me. I know how to connect it, and I know it wants to get to the ground and will kill you trying to do so. But I don't know how or why it does what it does.


Doug @ HomeWorks <- reluctantly admitting there's something I know squat about

This message was edited by deb1919 on 06/22/04 07:26.

Molecular orbital theory is definately a digression from the original post Larry, but I'd listen to that mp3 too! :P

I'd rather just type it, so here's a simplified version:

The electrons of atoms are layered in 'shells'. The first shell (from the nucleus outward) can hold a max of 2 electrons, the second 8, the third 18, the fourth 32, etc.

Unless ionized, the number of protons and electrons is always equal. Atomic number is the quantity of protons (and electrons); atomic weight is the quantity of protons plus neutrons.

As you keep moving through the periodic table and add a proton (and corresponding electron), you fill one shell, then start the next.

What determines whether the substance conducts or insulates is how close to full the outermost layer (the 'valence' shell) happens to be.

If there is only one electron (or sometimes two) on the outermost shell, it is bound to the atom very weakly; if the shell is full, or nearly so, the electrons are bound tightly.

The loosely-bound electrons can be knocked from the atom rather easily, and are then called 'free electrons'. A source of excess electrons can cause these free electrons to move along a conductive pathway.

Conductors are made of atoms with a large number of free electrons: copper, aluminum, gold, silver, etc. Insulators are made of atoms with few or no free electrons.

Simly put, this is electricity; the flow of electrons from a source, along a conductor, and back to the source. (Sources always have two terminals - one with an excess of electrons, and the other with a dearth of them.)

Larry
www.fineelectricco.com

About A.C.: Alternating Current differs from Direct Current in that the two source terminals alternate, or take turns, being the source of excess electrons.

Either A.C. or D.C. can be of high-enough voltage to kill, and either can be grounded to there is a potential (voltage) difference between a 'hot' wire and the earth (ground).

We use A.C. because it allows the use of transformers to step voltages up or down for most efficient use and the least waste of energy.

Since power (the work done) is the product of voltage and current [Watt's Law: P(watts) = E(volts) x I(amps)], you can raise one while lowering the other, and still maintain the power.

Long-distance power transmission is best done at high voltages, because the voltage drop along the conductors is dependent on the current [Ohm's Law: E(volts) = I(amps) x R(ohms)], not the voltage.

However, 'primary' distribution is easier at lower voltages (in the thousands of volts), as insulation is easier, and local utilization voltages are much safer yet, at 240/120(1 ph.), 208/120(3 ph.), or 480/277(3 ph.).

High-voltage/low-current circuitry requires a lot of insulation, whereas high-current/low-voltage circuitry requires a lot of conductor; usually, insulation is cheaper than conductor.

For example, look at the wiring under the hood of your car. The two largest wires are usually the battery cables and the spark-plug wires. The battery cables are mostly copper; the plug wires are msotly insulation.

The voltage-to-ground is the usual concern when it comes to personal safety. Rarely do non-electrically-qualified people come into contact with two (or more) hot wires; most accidental contact is with a single hot wire while grounded.

Larry
www.fineelectricco.com

to add to what Larry said...

The reason why copper is the best conductor of electricity is because it has one electron in it's outer valence shell, and it's easily knocked off.

Gold, interestingly enough, has a higher valence, and also has only one electron in it. It's also less likely to deteriorate than copper, making it more desirable as a conductor.

A couple questions if you guys don't mind...

Does the application of a potential cause an ionic change, and if so, is that what causes the electrons to migrate?

Also, which way do the electrons flow in a DC circuit? Some people say positive to negative, but I'm inclined to believe the opposite.



This message was edited by HDTVJunkie on 06/26/04 04:17.