# lightning

Discussion in 'Electronic Basics' started by [email protected], Jul 2, 2006.

1. ### Guest

When lightning strikes the ground, is the ground always more positive?

Why doesn't lightning ever go upwards?

Why is it unsafe to stand under a tree?

2. ### ChrisGuest

Hi, Bob. Most of the time, earth is more positive. However, "positive
lightning" (less than 5% of all lightning strikes) are the reverse.

Lightning goes both upwards and downwards.

Trees have hollow, water-filled cells, and as such can be a better
conductive path than the surrounding air.

There's quite a bit of good basic information in the Wikipedia article
on lightning:

http://en.wikipedia.org/wiki/Lightning

Good luck
Chris

3. ### Tim WilliamsGuest

You can calculate the voltage produced across a given width of ground (say,
the distance between your feet when standing!) when a lightning bolt
strikes. A couple ten thousand amperes can develop a lot of voltage,
especially with a fast event like a lightning bolt.

Tim

4. ### Robert RolandGuest

When the lightning current goes through the tree, the water inside the
wood instantly boils, causing the tree to explode like a bomb.