Question

what is resistance of air gap?

Answer 1

Electrical resistance of air is more of interesting concept. Instead, what is being used in the industry, which you might be aware of, is the breakdown/dielectric strength of air, used for design purposes of electrical protection equipment having their functionalities based upon this strength. There is almost no practical requirement of knowing the electrical resistance of air in electric industry but of breakdown strength of it, which is 21.1 kv/cm (rms) or 30kv/cm (peak) i.e you need 21.1 KV of voltage or more specifically, say electrical field to ionize 1 cm of air thereby letting the electrons to jump into the air and make it conducting.

So resistanceof air gap is high

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Answer 2

Generally, the resitance of an air gap is very high, approaching infinite resistance when measured with a convention Ohmmeter, which typically use a low-voltage battery as the source of current when measuring resitance. The low voltage will not excite air enough for it to reach the plasma state.
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