EDIT - This post has been edited from its original state due to the following whack on the head from @brainwagon (thanks :)) in the following form:
- For instance, when you say that the "lower the resistance, the faster the current can go through the material", it's actually the rate that the charge can be moved through the resistor that increases.
- Current and charge aren't the same thing: one ampere of current for one second moves 1 coulomb of charge (6.24E18 electrons). Lower resistance means that more electrons per second can move through the resistor. Lower resistance means more current can move through the resistor.
My interpretation: So instead of saying Current can move FASTER. It's that MORE current can move through given less resistance or more voltage, etc. On the other hand, Charge can move FASTER or SLOWER depending on less or more resistance, etcetc. It's like amount versus speed. Important subtleties!
I was gonna put resistance is futile, but if you've ever had to deal with resistance, you know it's not. I mean, maybe your resistance against resistance is futile, but it certain isn't. Chew your brain on THAT HAH.
So I jumped into this a little bit in earlier posts on series circuits when talking about the elements (or loads as engineers like to call em). And depending on the element's resistance to the current - or ability to keep it from moving forward - the element may have more or less voltage available for use. And therein lies the definition - blocking the flow of electrons to some degree.
Resistance is represented by R which is measured in ohms which is represented by the Greek letter Omega and measured with an ohmmeter. Kinda harkens back to how dumbly complex it is to explain current being measured in amps which is coulombs/sec.
Materials that have low resistance = do not impede current/the flow of electrons = conductors. Copper's good, salt water's good - so that's why PCB boards are copper clad. It allows for the free flow of electrons! (Hippie.)
On the other hand, materials that resist or prevent current are known as insulators like glass, wood, paper, plastics. You wouldn't see a pcb board made out of cardboard or maple. Maybe copper clad maple….
@atdiy: "I have a question, if you have a copper clad building, and lightning strikes it. And you're touching it. Will you get electrocuted?"
@whixr: "I don't think so, it's connected to ground. Lightning rods and all that."
@atdiy: "That's too bad. That'd be kinda cool…"
An example: Resistance tells us something about how much energy (voltage) you need when you move
currentcharge through an element, like a bulb. If you need lots of energy then the resistance of the bulb is high. If you don't need very much energy then resistance is low.
Another way of looking at resistance is to think about three bulbs with different resistances, each connected to 2 batteries. All three bulbs will have the same voltage across them but the current through them will be different.
For a given voltage, the bulb with the lowest resistance will allow for the fastest charge (larger current) and therefore glow brighter. And on the other hand, for that same voltage, the bulb with the highest resistance will prevent charge from flowing through as fast (smaller current) and will be the dimmest.
Okay - back to the section. There is of course a tenuous relationship between these three main things - voltage, current, and resistance - now known as Ohm's Law.
Current is directly proportional to voltage and inversely proportional to resistance
And I think the main thing is that this is relative to current and not to voltage. IE it should read "Current is directly proportional to voltage. Current is inversely proportional to resistance." Because this could theoretically be read as voltage is also inversely proportional to resistance, and that doesn't work…And once I figured that out, it was easy to derive these "truths".
"Truths" that arise from this statement (So qualified as there are qualifiers that may change such as the effects of temperature, conductor type, other elements such as capacitors/inductors/etc):
1) Resistance is the same regardless of current or voltage changes.
- Whether you change the voltage going to a material, or try to make electron charge go through faster, you'll still have the same amount of resistance in a given material to deal with. This may even increase or decrease with temperature changes.
2) A higher current means more voltage was made available.
- Or said in other terms, a higher voltage power source means that electron charge can run through a wire/conductor faster which means a higher amount of current can pass through. Doubling the voltage = double the current. Tripling the voltage = tripling the current.
3) The higher the resistance, the slower that charge (less current) goes through the material.
- As shown before with the light bulbs, if it has a high resistance to your power source, current can't push its way through easily - and this may lead to dimmer light bulbs.
4) The lower the resistance, the faster the charge (more current) can go through the material.
- Again with the previous example, if a light bulb has low resistance - and therefore excellent conductance - faster charge and more current can flow through easily and will most likely lead to a brightly lit light bulb.
5) The higher the resistance, the more voltage you need to push through current if you want to keep current speeds the same regardless of resistance.
- So the more resistance an element has, the more power you need to be able to push through current as much as if there were lower resistance. The power supply would have to be more powerful!
6) The lower the resistance, the less voltage you need to push through current assuming you want to keep current levels the same.
- With less resistance, you don't need as much power behind the current to get the current to move at the same amount. More efficiency!
And of course the equation itself:
E = IR
E being voltage….I being current (amperage)….and R being Resistance (ohms). Usually you have two of the components and just need to solve for the remaining one - a tiny bit of pre-algebra.