Ah im enjoying this too much... So i will discuss what resistance is:

Resistance is what it sounds like. It the opposing force to the flow of electrons in a conductor. This can be envisioned in many different ways. One whay is to see two buckets of water, held at same heights above ground with two equal length hoses tapped into the bottom of each. However one hose has a larger diameter than the other! (Less resistance). The water in this bucket will drain faster than the other one because there is less restriction on the path for the water to flow through to the ground.

In this example the resistance is due to the size of opening and surface firction between the water and the hose as it drains to the ground under gravity.

This analogy was deliberately introduced, because it also parallels the principal of Voltage and Current.

Voltage can be seen as the bucket of water held above the ground with the force of gravity pulling on it. There is a "Potential Force" due to gravity to pull the water to ground. In electronics, the gravity is replaced simplistically as magnetism, but formally refered to as the ElectroMotive Force aka EMF.

When the hose is tapped into the bucket of water, water falls to ground under gravity. The amount of water per second is entirely due to the resistance the water recieves to get to ground. The flow rate of the water falling under gravity, is a direct analogy to electrical Current flowing under the influence of a Electromotive force (or Voltage if you will).

To say we have x Litres per second describes a rate of flow. But physically it is not a real object. Its a measurement. So Current is ONLY a measurment of flow. But what does it measure?? The answer is Electrons. Current is the measured flow of electrons passing a point per second.


So how does this all tie in with the mysterious "Charge" i keep hearing about?

Well, to digress a second, could you imagin how much harder it would be to track your money if everything was in cents alone. (no nickles, dimes, quarters, dollars, etc). Really. Stop and think about this. It would be a nightmare! Now imagine your pennies were smaller than the radius of a Hydrogen atom! (5.29*10^-11 meters!). Well this is what its like trying to account for electrons. It sux really (you find yourself squinting alot). It didnt take long for people to measure groups of electrons, and you can thank Charles Coulomb for setting the standard:
"Here ye, Here ye, for now on, every group of 6.24*10^18 electrons shall now be known as a Coulomb!"


Later on, Andre Ampere set the standard that
One Ampere is exactly equal to 1 Coulomb of electrons passing a given point in exactly 1 second.


Now things are getting organized! But the locals kept complaining that their coulombs have no insentive to work for them. They keep laying around and pissing off the cat.

Electrons really are mean and grumpy entities. All they want to do is lay around and not do much. You force them to do anything, and they fight you all the way, trying endlessly to go back to being a sloth! Mr. Volt came along and observed this. He was an overweight man, and while fighting his electrons to do work for him, he discovered he was loosing weight! He did the math and discovered that he was burning one Joule of energy for every Coulomb of electrons he forced away from their happy place. He in turn defined a volt as:
1 Volt = 1 Joule of energy for every colomb separated from their "happy place" ;)


When you separate Coulombs of electrons from their usual life style, and they realize they can't get back, they get all mad and create electric fields ~ from where they are, to where they want to be. And this is a tool towards defining POTENTIAL DIFFERENCE or EMF. This is a comparison between the trapped and separated electrons, eager and energetic, and their untouched brothers, left to sloth and do nothing at all for you. Since the sloths will give up no energy for you, we say they are at GROUND, or ZERO potential of releasing energy. The separated electrons are at higher potential of releasing energy (if allowed to escape). The potential difference is thus one subtract the other!!


So who put all this together?

Well George Simon Ohm did. He was a rich man's son, and could afford to blow it on all the finest equipment! He eventually discovered one day while torturing his electrons by alowing them to return to ground only through a crapy and highly resistive conductor, that his tools were reading a constant amount of current would go through every time he allowed a Coulomb to take the trechorous path. Being spoilled and evil, he was not impressed with the electrons rate of travel. He felt they were being too cautious down the conductor and wanted them to bump, grind, and bleed when they get out to ground. He figured that he would double the number of coulombs trapped away from ground (Twice as much voltage), and let them push and shove twice as much to get home. Well he was right! Perfectly right! He noted that the rate of coulombs returning to ground (Amperes) was a perfect ratio to the Voltage created from all those Coulombs of electrons separated from ground. He origionally determined that this ratio was constant, no matter how many Volts he started with.

It was only when he changed his crappy old conductor for a meat grinder that he discovered that this constant can change! The crappy conductor was a walk in the park compared to this! And after killing hords of electrons, he learned that this ratio is a quantified measure of the amount of "evil" Resistance which gave his electrons.

He noted his law as follows:

1 Ohm (Muhahah) = 1 Volt / 1 Ampere


And ever after Resistance was clasified and thanks to Mr. Ohms evil practices, we have methods of testing and determining a materials resistance!

Mr. Ohm really did pull it together for us! His law ties Current, Voltage, and Resistance into one simple form. You want to figure out Current, well its Voltage/Resistance! You want Voltage, well its Current times Resistance. As well as his origional discovery, Resistance = Voltage / Current. ;)



Well Now you have it! NaN's world of electronics, and how Things came to be! Tomorrow i will show you how to use Ohm's law to make practicle circuits, and determine in design just how much Voltage and Current exists throughout a circuit.
:alright:
NaN
Posted on 2003-04-07 22:25:03 by NaN
Brilliant, amazing, out of the world tutorial !!! :eek:

I have always had to read this stuff out of books where they would plainly say Ohm=Volt/Amp and i just had to sort of mug it up. Noone ever really clarified those things to me.

It seems you have finally done it. Congratulations on the excellent work. Keep it up (in the same funny language :) ). I am looking forward to more of this stuff. :alright: '

Few (stupid) Questions -

1 Volt = 1 Joule of energy for every colomb separated from their "happy place"

Well if it is 1 joule of energy then why dont we simply refer to it in joules rather than in volts???

He figured that he would double the number of coulombs trapped away from ground (Twice as much voltage), and let them push and shove twice as much to get home.


Uhmm... by doubling the number of columbs, he doubled well columbs, right, so how did voltage get doubled?

And why exactly do you mean by "applying a voltage"? I mean what exactly are you doing when you are applying a potential difference?

The rest of the stuff is ok but i have never really been able to understand voltage.
Posted on 2003-04-08 07:30:22 by clippy
gladiator,

I see your confusion. Voltage is more embedded in science and was harder for me to 'detail' with some correctness.

1 Volt = 1 Joule / Coulomb

This means your right there is a direct connection between Energy and Voltage. However dont forget that its on a "per Coulomb" basis. Voltage is "stored" (or "spent" energy as you will see later) for every coulomb used. If it took more energy per Coubomb, The voltage will increase. Likewise if i can move three Coulombs with same amount of energy as before (1 Joule), the Voltage will decrease. Voltage is alot like the "static energy" you might hear about in physics, but applied on a per Coulomb basis.

Applying a Voltage on something is allowing the energy to be released from, or stored into, the object. Applying the Voltage on the crappy conductor allows the Coulombs to be released, and travel down it. As they bump and grind, the energy is released, when they reach ground they have no more enegy left. All their released energy was aborbed in the crappy conductor (and would heat it up to some extent).

Energy in never created or destroyed in our universe! It is FINITE. So Mr. Volt spends 1 Joule to move one coubomb away. The energy he spends is transfered into the coubomb, as it is trapped, and has the "POTENTIAL" of running back to Ground. Thus from where the Coulomb now sits, there is 1 V ( 1 Joule/ 1 Coulomb) of Potential within it. When released, the coulomb runs to ground a rate (current) that is proportional to the resistance of the conductor. The energy it once potentially had, gets transfered into the conductor (due to resistance of the conductor). The conductor has no means of storing energy, so it heats up, and the heat energy is transfered to its surounding air, and so on, and so on.

See how it all works. Mr. Volt actually invested energy, that eventually would turn to heat, through a chain of transferences. The energy he had was potential as well, stored as FAT! Fat which he ate from dead animals.. etc. etc. etc.

So when you buy batteries, say a 9V Dc battery. Somewhere, someone else invested energy into the battery on a per coulomb basis that resulted in 9V. You place it in you Radio, and it take the energy and transferes it into sound waves, and resisted heat. Pick anything in the universe and you can find a transference and storage of energy taking place! A Most obvious example is simply the ROOM TEMPERATURE!

So in short just keep saying to your self "Voltage is Potential Energy Available (or Used) on a per Coulomb basis"
Posted on 2003-04-08 18:42:41 by NaN
gladiator,

One last after thought!

Say your washing your dishes. And you find that different cups take different amounts of your scrubbing and energy to get clean. However at the end you find that you spend 100 Joules for 5 coffee cups. You decide to make a notation system for your self and declair "To wash one coffee cup it must average to be 100/5 = 20 Joules/Coffee cup" Since its a mouth full you come up with "1 Glad == 20 Joules/coffee cup".

Now you have a unit of measurement of energy needed to wash your coffee cups. Voltage is the same idea! The only difference is your "Glad's" are scaled 1:20 and Votage is scaled 1:1. Its as though Mr Volt wiped his hands when he was finished and said " 20 Volts = 20 Joule / Coulomb" ;)

I hope this helps a bit...
:NaN:
Posted on 2003-04-08 18:57:15 by NaN