Posted by Gerald J. on December 22, 2008 at 16:51:47 from (4.254.70.15):
In Reply to: Re: positive ground posted by larry cook on December 22, 2008 at 11:31:43:
There is no argument for either polarity that will hold water based on theories of current flow. Its convenient to think current flows from positive to negative, though we are pretty sure electrons do most of the work in electric circuits in metals by moving the other direction. Holes are only a factor in semiconductor crystals. Mathematically figuring positive to negative flow works out just as accurately as thinking negative to positive. Just keep track of the signs (and the units when mixing metric and imperial units).
There have been historical arguments but there were equally strong opinions for the opposing polarity at the same time. And engineers willing to put a whole car company on the line for their particular polarity. And both worked with no better or worse performance. The articles espousing either polarity will be found in articles from the Society of Automotive Engineers probably during the 1920s and 1930s.
I've worked with both polarities in electronics and vehicles so neither bothers me, or excites me.
There are two fundamental laws that work, no matter what. 1: The sum of the voltages around a closed loop is zero. E.g. the voltage rise in sources exactly equal the voltage drops in loads and wires.
2: The sum of currents though a node is zero. E.g. all the current that goes into a connection, leaves that connection, whether there are two connections to that node or a billion.
ALL circuit analysis is built on these two fundamentals. And it works every time and matches all experiments.
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