Why is plus on top?

[Paul Perry]

At 10:39 AM 17/04/00 +0100, neil johnson wrote:

>I think it dates back to valves.  Most valves have the anode at the top of the
>envelope mostly, I think, due to the construction of the device.  This leads to
>the natural step of drawing the valve with the anode at the top and the cathode
>at the bottom.  
Actually, most have a grid at the top. More than anodes, anyway.
And, if negative had been put at the top in schematics, valves wd have
been deawn 'upside down'.
I think it comes from the natural tendency to think + is "higher", like when
you label the side of a graph.
Of course, 'holes', lacking an electron, are a bit 'lighter', so....

Really, I think the fact that the 'large' voltages with respect to earth being 
positive in valve gear is what made the + on top convention stick.
You aren't gonna put those 'big' voltages on the bottom, are ya?
And, all that '+' electricity is trying to 'flow' to earth, and everything
flows 'downhill'.

paul 'downunder' perry melbourne australia