mcquinn you are correct in your formula above, here is a handy tool to help to remember this.
The wheel above is divided into three sections:
Volts V (on top of the dividing line)
Amps (amperes) I (lower left below the dividing line)
Resistance R (lower right below the dividing line)
X represents the (multiply by sign)
To use the wheel, just cover the unknown quantity and what is left is the formula to find the unknown.
Example:
To find the current of a circuit (I), just cover the I or Amps section
and what remains is the V volts above the dividing line and the R ohms (resistance) below it. Now substitute the known values. Just divide the known volts by the known resistance.
Your answer will be the current in the circuit.
The same procedure is used to find the volts or resistance of a circuit!
I have some pictures I took while reading the resistance of a couple of 510 and pennstyle attys
using a calibrated/certified and ISO approved Fluke RMS multimeter. I will post them as soon as I load them into the computer. To give you a heads up, a new 510 atty that has been used for only about a week read 2.3 ohms. And a 510 atty that has been used for about 4 months read 2.5 ohms. Note: both of these attys have been only used on a 5 volt big battery mod, with routine atomizer cleaning. Yes you read right 2.5 ohms after 4 months of use. This is why I love the 510.