# Why the electrical resistance of air is so high?

Why the resistance of air is so high?

Its resistivity is approximately $$2\times10^{16}\, \mathrm{\Omega\cdot m}$$.

Trying to compare that when I placed an electron, one in a copper wire and other in air: the one in air seems to be more 'free' than the one in copper wire. If this is not the case then what are those factors that classify air as insulator?

There are only very few free electrons in air, in stark contrast to the number of free electrons in the wire.

• ok,can i conclude that resistance takes into account the flow of charge due to charges of medium itself-not by the flow of external charges into the medium. only then the medium with lesser free electron will show more resistance? Commented Dec 10, 2016 at 18:00
• otherwise what will happen if we 'inject' some external electrons into both, copper and air, which will be more conducting? exclude 'internal' charges of media. Commented Dec 10, 2016 at 18:02
• If you inject electrons (or positive charges, or both, by turning air into a plasma, say) then its conductivity will indeed increase. In general electrical conductivity depends on availability (number density) of electrical charges and their mobility (resistance towards motion), roughly speaking.
– Pirx
Commented Dec 10, 2016 at 18:04
• so if i place two copper plates quite close, the chances of an (and only this) electron to jump accoss one plate to another is higher in 'ionised' air than normal air. the mobility of 'this' elecron is higher when air is ionised? or the mobility of 'a charge' increases when there are other charges around? @prix : thanks for answer Commented Dec 10, 2016 at 18:25
• Adding emphasis to what @Pirx said though, if you "inject" so many electrons into air that it becomes significantly conductive, then we stop calling it "air" and we call it "plasma" instead. Commented Feb 12, 2021 at 15:44

For current to flow it needs a complete circuit which would also be a complete path to ground. Copper is an excellent conductor because it has one electron in its most outer orbit that is pretty free to jump from one copper atom to the next. Air is the opposite. Not only are each molecule or atom air far apart from each other (more than a liquid or solid), but they are traveling very fast. Like 400 meters per second fast. So electric current which travels opposite the electrons themselves has to see a path from one fast moving oxygen atom to hydrogen to a nitrogen for example before it can plot the path to ground. The resistance is practically infinite. I believe you need something like 3 Million Volts to get to jump which is why lightening is so deadly.

Not exactly physics but from what I know about chemistry, metallic bonds (such as those found in a wire) displace electrons allowing more current flow but most everything in air forms covalent bonds which do not displace electrons.