Ohm's Law explained in layman terms.

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GrimmTech

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I see so many people asking about all the various properties of atomizer resistance and voltages and how this affects what is going on. I thought I would do a short (long) writeup for the people that do not understand how this works.

Conductors and how they pass current flow-
Conductors are anything that conducts electricity, or lets current flow. What ever the material is, its has a specific number of protons, and neutrons that make up the core with tiny electrons running around the outside. If there is a path from the battery to the ground (positive and negative side of a battery) current will flow. Current flows with the movement of the electrons on the atom. When you add an electron to an atom, it cannot hold more than it already has or it becomes another substance. So when it accepts the electron it passes one off the adjacent atom. This happens all the way down the wire until the last atom at the negative end of the conductor pushes one out. This is just like a pipe full of water. If you put in a drop on one end a drop comes out the other. If you put in 5 gallons, you get 5 out.

Resistance and how it affects current flow-
All materials have some type of resistance. Conductors have very very little resistance. Copper has almost none being a very good conductor. If you used a copper coil in your PV it would read it as a dead short (+ and - touching) and would let and extreme amount of current to pass and damage electronics not designed for such thing. The wire that makes up our coils has resistance to current flow. Resistance is how hard it is for electrons to pass from one atom to another. The higher the resistance of a material, the more voltage it takes to move the same number of electrons to make current flow. Again lets look at a water pipe. If you have a pipe that is 6 inches in diameter, it doesn't take much pressure to pump 100 gallons a minute. If you have a pipe that is only 1/4 inch in diameter, you would have to have a much greater pressure to pump the same amount of water. The higher the resistance of a material, the smaller the pipe.

Voltage-
Voltage is just like water pressure. The higher the voltage, the more current will flow across the circuit. It doesn't get much simpler that that.

What your atomizer does and how current flow affects it-
Your atomizer has resistance to current flow. Its hard for voltage to push the electrons through it. What happens is the friction of the electrons (just like rubbing your hands together) causes heat. As electrons jump from atom to atom, each atom is resistant to receive a new one and just as resistant to give one up. This causes your coil to heat up and atomize your juice. The less resistance, the more current will flow to heat it up. Fortunately, that all happens automatically. With the same voltage, (or water pressure), more flow will occur with less resistance (or with a larger pipe). So when you put in a higher ohm coil, it automatically cuts down the current flow and therefor the heat. This is why using a low ohm atomizer on an Ego works so well. You automatically get more current flow on the same voltage battery. When you get into VV or VW devices, it makes no difference. You simply add voltage pressure to get the current flow up to heat the coil to the desired point.

Now the Math-
* = multiplied by
/ = divided by
Everything we have talked about is really all about power. Power is just the complete output taking all things into consideration. Power (P) is rated in Watts.

Power = Volts * Amps
Power = Amps (squared) * Ohms
Power = Volts (squared) / Ohms

Voltage is rated in Volts (V)
Volts = Watts / Amps
Volts = Amps * Ohms
Volts = (square root) of Watts X Ohms

Current flow (I) is measures in Amps
Amps = Volts / Ohms
Amps = Watts / Volts
Amps = (square root) of Watts / Ohms

These are the formulas for calculating resistance, but its really not needed in this hobby because once we build an atomizer its stays relatively the same until problems start to occur.
Resistance (R) is measured in Ohms
Ohms = Volts / Amps
Ohms = Watts / Amps (squared)
Ohms = Volts (squared) / Watts


Overveiw-
Voltage is just like water pressure. More pressure = more water (current) flow.
Resistance is how big the pipe is. Smaller pipe takes more pressure to get more current flow.
Current is the amount of water flowing. Current is just a measurement of how much is flowing. The only way to raise this is to raise voltage or lower resistance. You cant change current alone without changing the other two.



I hope this is not an over explanation and someone that didn't understand this can now get a better idea.

Thanks for reading
Grimm
 

Cloud Wizard

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Nice description. Everyone goes through the learning curve. Once you start trusting the math and the science, an easy rule of thumb is simply resistance + 2 = ~8watts (e.g. 2.0ohm head + 2 = 4.0v = ~8watts / 1.5ohm head + 2 = 3.5v = ~8watts / etc...). Then just adjust what you buy for fixed batts, what you wrap for rebuildables, or settings on VV/VW to taste.
 

Baditude

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Very nice explaination, GrimmTech.

However, I just use this chart for a general guideline of either the resistance or voltage that I need, and also adjust the voltage to taste to the specific flavor being used at the time.

attyPowerChart.jpg http://imageshack.us/photo/my-images/689/unled66.jpg/
 
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johnms88

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Cloud Wizard

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Watts is the measure of work (power). In the vaping world it's roughly equated to heat produced. So if resistance goes down (with same voltage) or voltage goes up (with same resistance) power goes up and the work being done at the coil increases. For our purposes, when we find a "sweet spot" say at 8 watts, if we use a 2.0ohm resistance head we know to start at 4.0v to be close to where we want to be and then adjust by +/- .1 to account for unmeasurable differences in TH/Flavor/Vapor production.

The other thing these calculators can tell you is for your given settings, what current are you pushing. For a 100% mechanical mod it is somewhat irrelevant but for anything with an electronic switch there is an amperage limit (e.g. Provari V2 = 3.5A, ZMax = 5A, Vision Spinner = 2.5A - every device is different). This way we can buy a head device that maximises our usage (e.g. 1.5ohm dual coil will not go ever 3.8v on a Spinner even though the item is rated to go to 4.8v for safety reasons - it has reached the maximum amperage of the switch).
 
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