Without a unique definition for the word "electrcity," this discussion
makes no sense.
Well, there is no movement of charged particles through the air then.
The form of energy flowing through the air is not electricity but
electromagnetic radiation.
In most books the word "electricity" means electrical energy. Or
in other words it's 60Hz EM radiation being guided along a 2-wire
transmission line.
Search google for keywords "KWh of electricity." Then search
on "coulombs of electricity." The more common use by far is
electricity=energy. Therefore a flow of electricity is *not* an
electric
current, and a flow of electricity is measured in watts, not amps.
That can even flow through a vacuum where
there are no charged particles, molecules, atoms, or any of the usual
subatomic particles.
When electrical energy flows across a circuit from a source to a
load, it always flows in the region surrounding the conductors
and not inside them. The flow is described by the cross product
of the e-field and the b-field outside the wires. Inside the wires
the e-field is insignificant, and since the small field is axial, it
gives an energy-flow vector which is *inwards.* This makes
perfect sense, because wires become warm only because electrical
energy is flowing from the surrounding space and into the metal.
As for electricity to flow through air without sparking - that can be
done, although not often practically, and there is a name for that
phenomenon - "ionic current".
That's a flow of charge, not a flow of energy or "electricity."
Note that scientists have for the most part abandoned use
of the word "electricity" to mean charge. Faraday and Maxwell
may have used it, but since the early 1900s the textbooks
have dropped it. They no longer mention "quantity of electricity"
but instead call it "quantity of charge."
In an ionic current, charge is carried by
movement of ions. Where there are ions, there may also be some free
electrons available to move charge.
Ionic currents are usually less than 1 microamp.
Well, it's a current density. So a more appropriate measure
would be 1 microamp per square millimeter, or something. If the
ion drift is a meter per second, then this implies that a
microcoulomb worth of charged air can take the form of a
cylinder 1M long and ~1mm in diameter
If 1uA/mm^2 were a typical value for non-corona, then we could
silently transmit 100uA through a 1cm pipe, or 10mA through a
10cm pipe. Hmmm, sounds a bit large when compared to the
current on the belt of a classroom VandeGraaff machine.
They are hard to
target over major distances to anything other than a greatly isolated
conductor (such as a target in the middle of a room from closer to the
target than to the nearest wall, floor or ceiling).
Ionic currents mostly come from corona, although they could flow through
air ionized by ionizing radiation. If you experiment with sources of
ionizing radiation that are short of very significant health hazard, don't
expect 15 volts to push through more than a few nanoamps (and that may be
optimistic). And don't expect blacklights or UV LEDs to make air
conductive - doing that with UV requires wavelengths below 200 nm, maybe
well below (184.9 nm ozone-forming mercury wavelength may not work).
Nikola Tesla was putting vacuum bulbs on the top of small Tesla Coils.
They produce a fan-shaped visible glowing beam several feet long.
Today we would describe this as a pre-ionized path created by x-rays
then lit up by a few milliamps of high-freq current. With x-rays
involved, we can convert the air into a fluorescent lamp. Use it to
light up your bedroom and also light up your internal organs at the
same time. What fun!
((((((((((((((((((((((( ( ( (o) ) ) )))))))))))))))))))))))
William J. Beaty Research Engineer
beaty@chem.washington.edu UW Chem Dept, Bagley Hall RM74
billb@eskimo.com Box 351700, Seattle, WA 98195-1700
ph425-222-5066 http//staff.washington.edu/wbeaty/
