What is the voltage of a lightning bolt?

Question

PhysicsN, If it is raining and or moist air, I am sure the resistance to ground decreases...and the dirtier the air, the less resistance also, ....so that would be a lower voltage than dry air, right?

Answer 1

Here's some reading for you.

Answer 2

Since you have to make air a conductor, many 10s of millions of volts.

-Fred

Answer 3

The voltage of a lightning bolt (I assume you mean from the cloud to the ground) depends on how high the cloud is. It is a function of something in physics called the dielectric breakdown. The DB is basically how much voltage one needs in order to create an arc through the air. At standard temperature and pressure, this is about 3.3 million volts for every meter arced! By the way, when I say arc, I mean the visible flow of current through the air. So if the clouds are really high, it requires a higher voltage to arc to the Earth. Many lightning bolts are on the order of a billion volts from top to bottom!

*From your updated post: First I am the PhysicsNinja ;) That is true that the conductivity should go up just slightly when the air contains more water vapor. Also though, as the altitude gets higher, there is less and less air, and so also less conductivity. It is certainly not a linear problem, and a perfect answer would require some calculus and the differential conductivity function for the exact scenario. I still think the answer is a good ballpark answer for Yahoo Answers.