Re: SHOCKING!

[Mike Curtis <wd6ehr@xxxxxxxxxx>]

> 
> As a certified technodolt, I enjoyed - and profited from - Mike's
> Electricity 101.
> 
> But, one question. This is not an attempt to skew the thread onto a
> trivial tangent; I'm just curious. Don't those birds have BOTH feet
> on the power line? If people get a volt jolt when they grab the line
> with their left hand, why don't birds get same when they plant their
> left foot?

I've not payed that close attention to the very high voltage lines, but 
have heard from others thad birds sit on these using just a single foot.  
However, even if they planted both, the voltage drop across a couple 
inches of large diameter copper wire would be insignificant.

A return to pre-algebra for a moment:

Current only flows when there is a DIFFERENCE in voltages.  If you have 
440,000 volts on the left foot and 440,000 volts on the right foot, you 
have an algebraic difference of 0 (440,000 - 440,000 = 0), and therefore 
no current flows.  We call this "common mode" when dealing with a 2 wire 
balanced circuit (e.g. telephone line), where we require a voltage 
DIFFERENCE for a signal, e.g. 5 volts on one wire and 4 volts on the 
other; or 105 volts AC on one and 105 volts AC @ -180 degrees phase on 
the other.

Think of this like an old fashioned balance scale.  You put an ounce om 
each side and it's balanced.  If the scale's strong enough, you put a ton 
on each side and it's still balanced.  But take an ounce from the ton and 
it tips.

If we push each other with 100 lbs pressure, we stay in one place.  If I 
push you with 50 more pounds pressure than you push me, then you move 
backward.

Voltage doesn't matter.  It's voltage DIFFERENCE that counts.

Grounding all your equipment doesn't eliminate voltage.  It minimizes 
voltage DIFFERENCE.


 -- mike