 |
 |
Charged Droplets and Dust
Name: Mike C.
Status: other
Age: 40s
Location: N/A
Country: N/A
Date: 10/27/2003
Question:
My question is, we have water being passed thought fine nozzles at pressure,
the water droplets are less than 50mu, we then blow the water droplets into the air to make
a fog, very similar to a snow making machine, I was trying to make a correlation between
positive and negative charges, to say that the water droplets are charged and therefore
the negative dust particles would be attracted to them, is there a science behind that
theory?
Replies:
There is a lot of science surrounding the behavior of small droplets (solid or liquid). As
the diameter of a particle decreases below about 0.1-0.2 microns (100-200 nanometers) two
properties that are usually negligible become dominant and one property that dominates the
behavior of matter becomes increasingly negligible. The surface charge and the surface
tension become increasingly important, and gravity becomes decreasingly important. As a
result some strange things happen. Dust "clouds" become stabilized because the particles
repel one another and Brownian motion (explained by Albert Einstein) keeps them in motion.
This makes these small particles able to pass through cell membranes and / or be deposited
permanently in the lower lungs and pass directly into other cellular tissue. In addition
the surface energy increases as approximately 1/R where R is the
particle diameter. So even liquid particles can "bounce" together but not coalesce. If you
wish to enter this fascinating world of small particles search the terms: colloids, colloid
chemistry, or colloid physics and you can find information at any level of sophistication
you wish.
Vince Calder
Mike,
Indeed, if one can produce water droplets with a charge opposite to the charge borne by
dust particles in the air, there would be a mutual attraction between them. Although water
molecules are electrically neutral, they do have a dipole that results in the oxygen atom
bearing a slight negative charge -- the region near the hydrogen atoms bears a corresponding
positive charge of equal magnitude. When water molecules coalesce into a droplet. the
droplet is likewise electrically neutral.
How does your spray technology impart a net (+) or (-) charge to the droplets? How do you
determine the polarity of the charge on the droplets and dust particles? In other words,
how do you know they are of opposite charge? These questions must be addressed before one
could posit facts supporting your hypothesis, " ...trying to make a correlation between
positive and negative charges, to say that the water droplets are charged and therefore the
negative dust particles would be attracted to them."
Regards,
ProfHoff 737
Click here to return to the Physics Archives
| |
Update: June 2012
|
|
