MadSci Network: Physics

Re: In water, what path does electricity take?

Date: Wed Feb 2 12:25:59 2000
Posted By: Chris Seaman,
Area of science: Physics
ID: 948992955.Ph

Water is a conductor, like a metal, just not a very good one.  Therefore, 
just like in a conductor, the current (flow of electricity) takes the path 
of least resistance.  Because you are asking about water, I'm assuming you 
are thinking of a large body of water, such as a swimming pool or lake.  In 
a large conducting medium, there are many different "paths" for the 
electrical current to spread out over.  For example, if an electrical 
source (such as a toaster) were dropped in the center of a circular 
swimming pool, the current would flow from the center outwards, uniformly 
in all directions.  The density of the current would be highest near the 
source and decrease as a function of distance from the center (the radius).  
This problem is easy because of the symmetry of the swimming pool and 
because the electrical conductivity is uniform in all directions.  These 
problems get more complex as the shapes get more complex (a kidney-shaped 
swimming pool) and elements enter the system which change the uniformity of 
the properties (a floating pool sweeper with a metallic hose).  Maxwell's 
equations (complex partial differential equations) are used to solve this 
type of problem, but the math gets very ugly very quickly.  A good, basic 
description can be found in a physics text book such as Sears, Zemansky, 
and Young, or Halliday and Resnick, in the chapters which discuss 
electricity and magnetism.
Chris Seaman
Alcoa Technical Center

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