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RE: Physics of Wireless Transmission



Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Dave,

This page explains it better than I can:

http://hyperphysics.phy-astr.gsu.edu/Hbase/magnetic/magfield.html

Cheers,

        Terry


At 09:04 AM 4/24/2006, you wrote:
Hi Terry,

> >I have found a web page that presents the mathematics behind
> >relativistic charge:
> >http://physics.weber.edu/schroeder/mrr/MRRtalk.html
> >
> >You will note in equation 3 it says, "The expression in
parentheses
> >must be the magnetic field strength."  When you work out the
actual
> >dimensions for the term in the parentheses, you get mass per
time,
> >which is not the unit of magnetic field strength.

I knew I had worked this out before and double checked my work in
the past.  Look at this:

> Let's check it out...
>
> http://www.greenfacts.org/power-lines/toolboxes/magnetic-field
> -units.htm
>
> """"
> Magnetic Field Intensity Units
>
> The International System (SI) unit of field intensity for
> magnetic fields is Tesla (T). One tesla (1 T) is defined as
> the field intensity generating one newton of force per ampere
> of current per meter of conductor:
>
> T = Nw . A-1 . m-1 = kg . s-2 . A-1

The above is incorrect.  The web site is also incorrect.  The
tesla is a unit of magnetic flux density, not magnetic field
intensity (strength).  Magnetic field intensity (strength) is:

Coul / m * sec (in MKS units)
A / m (in SI units)

To resolve our disagreement in understanding units, we need a
more authoritative source for the definitions of units.  I use
NIST:
http://physics.nist.gov/cuu/Units/units.html

As I mentioned before, the relativistic charge equation produces
the wrong units for magnetic field strength.

I have noticed that many different authorities do not properly
understand the difference between magnetic flux density (tesla,
gauss, B field) and magnetic field strength (H field).  They are
often erroneously interchanged in order to get the desired
results.

Dave