MadSci Network: Physics
Query:

Re: How does atmospheric pressure affect electronic resistance?

Date: Wed May 28 21:21:08 2003
Posted By: Dwayne Rosenburgh, Senior Electronic Engineer
Area of science: Physics
ID: 1053610666.Ph
Message:

For "ordinary" Ohmic resistance, there needs to be a medium for the 
electrons to flow through.  In that environment, a vacuum is like an 
insulator and no current (i.e., electron flow) exists.  However, not all 
currents and resistances are Ohmic -- an example is the semiconductor.  
Therefore, it is possible to have a current across a vacuum.  One way to 
accomplish this is to break the vacuum, temporarily, by applying enough 
potential difference (voltage) to the "sides" of the vacuum.  In practice 
a perfect vacuum cannot be created because all the materials that would 
surround such a space have a finite pressure, which means that they expel 
some atoms or molecules into the space.  Applying a (large) voltage to the 
surrounding material increases the pressure and causes electrons to flow.

A second method to accomplish "electron flow" through a vacuum would be 
via the photoelectric effect.  Photons can travel from one side of the 
vacuum, through the empty space (recall, that photons do not need a medium 
through which to propagate) and liberate electrons on the other side.  
These liberated electrons are called photoelectrons.  Since the effect is 
that electrons are moving from one side of the vacumm to the other side, 
there is a current through the vacuum.  Perhaps, it is more correct to say 
that energy flowed through the vacuum.

I see no reason why just a decrease in atmospheric pressure would have an 
effect on resistance, but a decrease in pressure and matter will effect 
Ohmic resistance.


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