MadSci Network: Engineering

Re: Antenna and equal but opposite curents?

Date: Fri Dec 4 08:56:44 1998
Posted By: Rick Cousins, Regional Mgr/Chemist-Industry
Area of science: Engineering
ID: 910158638.Eg

This deserves a better answer than I have time or space to give you.
A faulty analogy would be to think of an light bulb. Current in and
current out but energy loss thru electromagnetic radiation. The fault
of the analogy is of course that the radiation is a function of the
filament heating and not direct RF loss (though a new energy saving
light does work thru microwave emissions).  Any charge in motion will
generate em radiation, something that caused folks to initially challenge
the 'solar system' view of atoms. Since moving charges emit radiation,
they argued, the electron should spiral into the nucleus. It turned out
that the solar system model was much to simplistic and that electrons
do not radiate just because they are associated with a nucleus to form
an atom. But the principle that moving charges set up fields is still
valid. An antenna is by design the most efficient way we know to 'leak'
this em radiation into the environment. The shape of the antenna varies
with the desired wavelength and physical constraints. So you will notice
those which look like rakes, loops, circles, dishes, pizzas, pencils,
pigtails, and more.‰

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