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Name: Steve R.
Status: other
Age: 40s
Location: N/A
Country: N/A
Date: 4/9/2003


Question:
How is the movement of electricity through air different from its movement through a copper wire?


Replies:
For electricity "to move" electrons must be transported in some manner or other. The electrons in a metal, the so called conduction electrons (which are the same outer electrons that chemists talk about when they refer to "valence electrons") -- these electrons in a metal are not bound by any single nucleus and are more or less free to move in response to an applied voltage. In air (or any other "non-conductor") the electrons are bound to various atoms and/or molecules and are not "free" to move in response to an applied voltage. Not "free", that is, until the voltage is so high that atoms and/or molecules are ionized. Then the electrons and ions are "free" to move. There are many things that can affect this -- moisture, dust, radioactive particles, ... the list is long. It does not take very many so-called "charge carriers" to reduce this "breakdown voltage" drastically, and if the current is high enough to form a plasma, which is essentially a conductive gas. The electrical resistance of liquids and non-metallic substances fall in between. Here the movement of electrons can be very complicated. I do not recall the exact numbers, but I do remember that the resistivity of pure water decreases by a factor of 10 between 0 C. and 40 C. just because water is ionized ( H2O -----> H(+1) + OH(-1) ) at the higher temperature.

Vince Calder


Steve,

It is not actually electricity that moves through wire and air, it is electrons. Electrically charged particles move through material. Electrons are the most common moving charges.

Every copper atom has one very loose electrons. This is true of all metals. This is what makes them metals. In a copper wire, the energy due to room temperature is enough to break many of these electrons free. They float around inside the metal. When connected to a battery (or outlet), the power source pushes the electrons. They move through the wire like a continuous loop of charge. The atoms themselves stay put.

Air does not have loose electrons. Air molecules tend to move as units. Since the air molecules have a net charge of zero, The battery pulls the electrons one way and the protons the other. Unless there is enough energy to pull the atoms apart, like lightning, there is not much movement of charge at all.

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College



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