I've worked with Ohms Law for decades and the formulas don't always stick in your mind when time passes. Print this chart to refer to and let the formulas sink in and begin to make sense. There's one in each quadrant that you will find more applicable to the way you work. Memorize one from each sector. Using the ohm's law calculator is quick and easy, but it doesn't provide insight into the relationships of voltage, resistance, and current.
http://diyaudioprojects.com/Technical/Ohms-Law/
Think of electricity in terms of water pressure and volume.
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Voltage is pressure, just like the PSI water pressure in a hose. In an ecig, higher voltage pushes the electrons faster through the wire, creating more heat or less heat as you raise and lower the voltage. You find the voltage by multiplying the resistance x the current. V=R*I.
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Amperage or current is volume, like the gallon per minute rating of water flow. Amperage in an ecig refers to the relationship between wire gauge and voltage. I (amps) =V/R or voltage divided by resistance.
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Resistance is analogous to the way water is slowed down by drag inside the hose or a water pipe. The longer the hose, the more it restricts water volume that can travel through in a given time. Resistance is found by dividing Voltage by the Amperage R=V/I
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Power is a term that describes the rate that energy is moving through a wire. It's a relationship between voltage, current, and resistance. If you know two, you can calculate power in watts: P=V^2 / R. In most ecig calculations. We know the voltage and resistance.
It's really that simple. If you know two of the three, you can find the third.
If you are vaping a 2 ohm coil at 3.7v, you are producing 6.845 watts (P=V^2/R) and 1.85 amps (I=V / R).
Play with this for a while and it will begin to make sense (especially if you run some numbers and then use the ohms law calculator to see if you match results with it). Doing that will increase your confidence as your calculations begin to match the online calculator.
