Re: Magnetic field and relative motion
From: Pmb (someone_at_somewhere.com)
Date: 06/19/04
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Date: Sat, 19 Jun 2004 19:56:32 -0400
"V.K.Tamhane" <vktamhane12@rediffmail.com> wrote in message
news:9d62a326.0406190505.6c62c7d0@posting.google.com...
> "Pmb" <someone@somewhere.com> wrote in message
news:<ZoudnVo-N6WrIk_dRVn-hg@comcast.com>...
> > "V.K.Tamhane" <vktamhane12@rediffmail.com> wrote in message
> > news:9d62a326.0406180018.2eca638b@posting.google.com...
> > > "Pmb" <someone@somewhere.com> wrote in message
> > news:<ir2dnYsAgfel9kzdRVn-tA@comcast.com>...
> > > > "V.K.Tamhane" <vktamhane12@rediffmail.com> wrote
> > > >
> > > > > 1. Observer on the disc will notice magnetic field rotating along
with
> > > > > the circuit and so seen from this frame, there is no emf generated
in
> > > > > the circuit of stationary frame.
> > > >
> > > > It is incorrect to think of magnetic fields as rotating as you
> > mentioned.
> > > > Doing so can lead to serious errors.
> > >
> > > What errors?
> >
> > Errors in calculations of the electric field. E.g. if you consider the
field
> > to rotate with the magnet and define the E-field as F/q then the
divergence
> > of E will not vanish outside the magnetic in empty space, thus violating
One
> > of Maxwell's equations, i.e. div E = rho/e_o where e_o is the
permitivity of
> > free space.
>
> Magnetic field never produces electric field. My articles
> No.3,4,8,9,12 and18.
>
> > It also makes meaningless the field where the field velocity is greater
than
> > the speed of light.
>
> Define the concept of field.
You're not familiar with the concept of a field? A field is an association
of an element of a set with an element of another set. E.g. an electric
field is an association with a point in space at a given time with the
quantity E defined as
E = lim (q->0) F/q
where q is the charge on a test particle and F is the force on that
particle. There need not be a particle at that point for the electric field
to be meaningful. The field itself as an existance beyond that since the
field itself carries momentum. Since there is a one-to-one correspondence
between the E and something physical (i.e. found in nature) then the field
itself takes on a physical meaning.
You call it a mathematical abstraction but you've not justified your
comment. You make this comment as if the field itself doesn't exist or has
no meaning. I see nothing in your comments to justify it. You made the
claime that only forces are measured and I see no attempt by you to support
your claim. For is not a quanity which is directly measurable. All
measurements in physics are kinematic. None are dynamical.
> Where is the field if there is no test charge?
Where is my sister on her birthday. Sorry but you'll have to be more
specific. Besides, fields are not always localized quantities. e.g. Where is
the Earth's gravitational field?
Pmb
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