[TowerTalk] Is lightning hitting the tower..or the yagi's

[Roger (K8RI)]

On 6/24/2010 10:43 PM, jimlux wrote:
> Andy wrote:
>    
>>      
>>> In 'normal' lightning it is a 'negatively charged downward leader' that
>>> comes out of the cloud.  It progresses in 50-100m jumps as the charge pushes
>>> it down... Note, I said PUSHES, the ground influence on the leader direction
>>> is relatively small, it is the gross field gradient between the earth and
>>> cloud that causes the major movement groundward at about 1/3c.
>>>        
>> Amazing that it can accelerate and push particles close to relativistic speeds!
>>      
> the particles aren't actually moving, it's charge flowing.  Just as the
> electrons in a wire don't actually move at the speed of light, though
> the EM wave does.
>    
I always liked the pool ball analogy. You put a row of pool balls 
together so each one touches its neighbors. Then strike one end of the 
string with the q-ball. The q-ball stops, the string appears stationary, 
but the ball on the opposite end takes off instantly and at nearly the 
speed of the q-ball. The The point is the ball on the end of the string 
departs almost the instant the q-ball strikes.  Yet the q-ball would 
have to be traveling many times its actual speed to get to the end of 
the string by the time the other ball leaves.

In a conductor where the number of free electrons can be assumed to be 
100% then using Avogadro's number which IIRC is 6.022 X 10^23 molecules 
per gram molecular weight (figure varies some what with the age of the 
text book), the cross sectional area of the conductor, and the current 
in Coulombs, you can figure the actual speed of the electron drift 
(average speed of the electron flow)  There is no guarantee that any 
specific electron entering the wire will ever leave.  Even though the 
electron flow is on the order of a few inches per second the circuit 
behaves as if they were moving at close to the speed of light.

73

Roger (K8RI)