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First post - two questions :D

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ComputerPsi

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Hello all. I don't know how long I'll be on this forum.. I guess it depends on the answers I get here.. well anyway, here are two questions:
1. I have studied electronics for quite some time, and have read through different books and tutorials. Some use the conventional method saying that positive goes to negative. Others use the "newer" method where negative goes to positive. Then some guys start confusing is saying that there are "holes" and "charge carriers" that either hold an electron, or a hole.. And then there are guys that say stuff comes from the negative AND the positive. Well, I basically understand the reasoning of all of them (except the last one)... my main question is this: Are all of these just theories has there actually been something proven? If all are just theories, the authors seem to be using them as facts. If something has been proven, then the other authors are incorrectly teaching just because they can visualize/explain it better?
2. Unless using a transistor, in my experience, I have found that voltage and resistance rules the circuit. You then use ohms law to figure out the current. However, the world is not perfect and a power source cannot produce an unlimited amount of current (presently). So, I am guessing that when too much current is asked for, the ohms law work in reverse, and you have to find out the voltage. Either that or you start breaking ohms law.. But anyway, what happens when, with a limited current, you have a parallel circuit? In theory, ohms law works out that all the current is divided out, depending on the voltage. If there is not enough current, something strange happens..? I tried looking it up in different tutorials and everything... I didn't find it anywhere. Anybody know what happens?

Well, yeah.. I would be greatfull if anybody could answer my questions. I was wondering about them for quite some time.
 
Free electrons are charge carries, and holes are also charge carriers "Holes" are just that, locations in an atoms electron cloud that should normally contain an electron but don't have one, they're predominantly refered to in semi conductors because holes aren't usually a majority charge carrier, a hole doesn't have as much of an energy transfer potential as an extra electron does. Electron flow in a metal wire is almost exclusivly free electron flow, an electron is pushed into one and one pops out of the other end. Contrary to popular thinking they don't get injected into one end and shoot through the entire length to exit the other end, it's more like water flowing through a pipe, but with metal the pipes are always full of water even when not connected to a voltage source. The voltage source just causes electron pressure which causes gradual flow. Oddly enough the electrons (A negativly charged particle) comes out of the positive lead and heads in the direction of the negative lead, holes would travel in the opposite direction. When you get materials liked doped semi condcutors together the P (electron surplus) and N (eletron deficiant) materials and their boundry layer causes some weird effects.

The voltages and currents in a circuit ALWAYS equal out you can't break that rule, if you come up with a result that doesn't make sense it's an improper calculation. Could you show us some example schematics of what you're refering to when things don't add up? The real world is frightfully more complicated than simple schematics make it sound so things sometimes don't seem to add up but believe me in the end every single last electron is acounted for.
 
I almost forgot to post a link. This site contains some of the best tutorials I've ever found anywhere on how electricity really works, semi conductor theory and how transistors actually function. It's written so a layman can understand it so it might seem a bit simple but it contains a lot of very useful information.

http://amasci.com/elect/elefaq.html
http://amasci.com/amateur/transis.html
 
1. Let's clear this up for you. There are two kinds of current flow, conventional flow and electron flow. Electrons have a negative charge. But in circuits it is just math, and in math there are "conventions". It doesnt matter what the convetion is as long as it stays the same.

In conventional current flow, it goes from + to -.
In electron flow, it goes from - to +.

Conventional flow is what is used since it's been around longer and things don't like to change. But we know electron flow exists. But what is conventional flow then? Conventional flow is also called "hole" flow. A hole does not have + charge like a proton, but is rather the absence of a negative charge. When an electron moves from one area to the next, it leaves behind an empty opening called a hole. If you visualize an infinitely row of electrons with one gap moving, and each electron is moving left by hopping into the gap (and therefore leaving a gap behind it for the next electon to hop into), the gap will appear as if it is moving to the right while the elctrons are moving to the left. This gap is the hole and therefore moves in the opposite direction of the electrons.

2. To account for a how a power supply behaves when it cannot provide the current required, you have to examine how the power supply itself works rather than just a little symbol on the page. In most cases (all actually that I know of) the power supply will either

-be destroyed due to overheating
-or it's output voltage will drop as it tries to supply more current. THe voltage dropping will reduce the current that the load is drawing due to I=V/R. This will continue until I and V balance out reach steady state. Remember that during the transition period, the currents and voltages cannot change instantly. They all move smoothly from one point to the next (even if it's very very fast). What this means is that the current being draw doesn't instantly rise up to I=Vinitial/R so that there is a single instant in time before the Vinitial starts to drop where the equation does not hold. I must go up smoothly towards I=Vinitial/R, and as it reaches the current limit from the power supply, V will start to drop which will slow down the rise of I until V and I reach equilibrium.

What this means is that if you have an ideal voltage source and two parallel resistors, the current will work itself out. If you have an ideal current source instead of a voltage source, the voltage across the resistors will work itself out based on the current in the resistors. If you have a non-ideal voltage source, due to the internal workings of the power supply which will vary and is more complicated than the two resistors, the voltage will being to drop as the current exceeds the maximum that can be supplied. The act of dropping the voltage will cause the current to drop in turn due to I=V/R.

other authors are incorrectly teaching just because they can visualize/explain it better?
No, they are teaching it like that so YOU can visualize it and understand it better. Have you ever heard the saying, teaching is the act of lying a bit less each time? Otherwise you would start out with quantum mechanics rather than V=IR.
 
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Just a quick question in reference to this, since this post does such a good job explaining the difference between electron/conventional flow...what is a good way to visualize which are "input" and "output" pins on say something like a diode that is not necessarily tied to ground. I get confused because of "potential", which can make a difference?
 
The current (electron flow) in a diode always goes against the arrow, that is, into the cathode and out of the anode.
 
Conventional flow "exists" because Benjamin Franklin got it wrong. As noted above, it doesn't really matter from a circuit analysis point of view.
So, I am guessing that when too much current is asked for, the ohms law work in reverse, and you have to find out the voltage. Either that or you start breaking ohms law..
No. Ohms law stands firm. If you short a battery out, infinite current does NOT flow because of the resistance of the wires and the resistance of the internal parts of the battery.
 
Even in super conductors the IMPEDANCE of the circuit has to be taken into account. Simple law of physics. Work can not be done with zero energy.
 
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