Thanks for the explanation afstfm.
Free electrons repel each other like crazy, so their behavior is rather predictable. They travel on the outside of conductors because that is where it is easiest for them to move and they can get the furthest away from each other. For round conductors, the smaller diameter the conductor the more electrons that can fit per surface area.
To illustrate this to yourself, draw two circles, one with a circumference of one inch and one with a circumference of two inches. Now get a bunch of dots from your paper hole puncher and set them around the outside of the circles just touching each other, and just touching the line of the circles. Does the larger circle have exactly twice as many dots as the smaller circle? No, it has fewer per inch. And if you repeat the experiment
putting dots on the line Inside the circle you will see that many fewer fit inside the same size circle than did outside.
This is part of why the wires for your lightning
ground system cannot have curves with radius tighter than eight inches, nor bends greater than 90 degrees. When the electrons are forced to bunch up or turn away from their heading to ground they jump off the conductor onto an easier path to ground and that is called a Side Flash.
ground FYI: Copper braid is not permitted for lightning ground systems - the electrons must make many direction changes, and copper ribbon is not permitted because so few electrons can fit on the surface as compared to the same amount of stranded wire. Also, both are prone to surface corrosion
, which causes massive resistance. If you ground your shrouds be sure to ground the CHAIN PLATE
and not the backing plate - grounding the backing plate does not work because the current
must make two 90 degree turns through the bolt at two very inadequate connections.
Very interesting - thank you for sharing that! I see Mr Emanuelson states that good conductors such as Cu or Al must be used to construct the Faraday cage - but his brief address of the difference between a Faraday cage and an electromagnetic shield cleared up my confusion about protecting electronics
from induced current
- for lightning protection you want an electromagnetic shield, not a Faraday cage to protect your laptop/electronics. Be careful about your interpretation of the article - he uses "Faraday cage" interchangeably with "electromagnetic shield" - too bad, because otherwise the article would make more sense to people without a background in physics.
But I *still* don't know whether I am supposed to have the shiny side of the tin foil on the inside or outside of my hat.