Difficult Conversion........

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Difficult Conversion........

Postby Guest » Fri Feb 24, 2006 4:02 am

Not sure if it is possible. But... does anyone know how to convert Volts to w/m^2????
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Postby Guest » Fri Feb 24, 2006 8:31 am

It is not. Under slightly special circumstances it is possible for a radio wave having a known electric field strength in V/m.

Generally, the power vector (also called Poynting vector) of a radio wave or and e-m wave is the vector cross product of the E field and H field. For a plane wave in free space, there is a fixed atio between these called the impedance of free space, usually represented by Z-sub-zero, which I can't represent here. It is about 377 ohms. (If there are any reflections or standing waves, this is not true)

For a propogating plane wave power density in W/m^2 is equal to the E-field ( in V/m) squared and divided by Zo.
S = E^2/Zo

This relationship is commonly used in calculating exposure to radio waves, which can injure by inducing heating if sufficiently high powered (that's what microwave ovens do, only we call it "cooking")
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