2011/9/9 mark springer : > unit resistivity per area/length > > resistance has to be ? expressed over a Volume. can you have > dimensionless resistance that is not infinite? I do not see it Resistivity of metal films used for capacitor construction is measured in ohms per square, and it is dimensionless. See here for a good explanation: http://www.esdjournal.com/techpapr/ohmmtr/ohm.htm I don't know how that relates to water though, which would have to be ohms per cube. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .