October 26, 2008: Electric Fence

[tw]

Originally Posted by glatt

I understand that in a fence like this, a strong current can be induced during an electrical storm, even if the fence itself isn't struck. When lightning strikes even a few hundred feet away from the fence, it radiates an electromagnetic field, and as that field passes by the fence, a current is induced in the fence wire. The stronger and closer the lightning strike is to the fence, the stronger the current.

Which makes complete sense until we apply numbers.

If a nearby strike could induce currents that high, then devices designed to maximumize those currents would always be destroyed by nearby strikes. How many cell phones and car radios are routinely destroyed by nearby strikes? Zero.

Campers were sleeping near a tree that suffered a direct lightning strike. Those who were sleeping parallel to the tree were unharmed. Those who were sleeping pointed towards the tree were rushed to the emergency room. Follow the current (just like diagnosing hum from a computer). Current was down the tree, through earth, into the campers head, out via his feet, then outward in earth. Best electrical path was the longest distance through campers who were not parallel.

Same applies to four legged animals that are at even greater risk. Common is for a nearby tree to be struck. That current takes a shorter path by rising from earth into a cow's hind legs. Back to earth on fore legs. Path through a cow is the most conductive path which is why a tree struck 30 feet away also electrocutes nearby four legged animals.

What should be located on golf courses? Shacks surrounded by a buried copper wire loop so that lightning currents in earth need not kill by traveling up one leg and down the other. Instead the buried loop makes an electrically shorter path.

Damage from nearby fields is common when myths get promoted as fact. If nearby fields were so deadly, then every nearby baby monitor and smoke detector were also destroyed.

Only fact was that cows were electrocuted. Was a tree just behind the photographer? Currents down that tree and through cows may have been seeking charges located somewhere on the horizon of that picture.