Hi Jason:
Water comprises a 3-dimensional resistor.
The value of the resistor depends on:
* the "purity" of the water itself (the
resistance is inversely proportional to the
purity);
* the dimensions of the electrodes (i.e., the
conductors in contact with the water);
* the distance between the two electrodes;
* the cross-sectional dimensions of the current
pathway;
* other conductors in the water (which may short
out some of the water, or may carry some of
the current to another load).
The hazard of water is that it displaces air
insulation in typical electrical products.
Most products rely on air insulation for both
performance and protection against electric shock
(which is why safety standards include minimum
dimensions for clearance). If water displaces the
air insulation, then an unintended current path is
created. If the body happens to touch that water,
then the unintended current path may include the
body.
If your colleague understands that air is commonly
employed as an electrical insulator (e.g., overhead
power lines), then I would hope that he could
understand that water displaces the air, and thereby
provides an unintended (and uncontrolled) conductive
path.
(Most of your examples are examples of water displacing
air insulation.)
Water on the skin tends to enlarge the electrical
connection to the body. The larger the area of
electrical connection to the body, the more susceptible
the body is to the same value of current.
(This explains your "leakage" paragraph.)
Best regards,
Rich
ps: Is there a value (or range of values) for the
resistance of water? Is there a standard way of
measuring the resistance of water?
-------------------------------------------
This message is from the IEEE EMC Society Product Safety
Technical Committee emc-pstc discussion list.
Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/
To cancel your subscription, send mail to:
majord...@ieee.org
with the single line:
unsubscribe emc-pstc
For help, send mail to the list administrators:
Michael Garretson: pstc_ad...@garretson.org
Dave Heald davehe...@mediaone.net
For policy questions, send mail to:
Richard Nute: ri...@ieee.org
Jim Bacher: j.bac...@ieee.org
All emc-pstc postings are archived and searchable on the web at:
No longer online until our new server is brought online and the old
messages are imported into the new server.
