Inquiry about the definition of a GAUSS
tom...@tc.fluke.com
force per cm2. The more lines of force, the stronger the magnetic field or
flux.
The question I have is this: How on earth can one measure lines of force?
As a kid I remember pouring iron filings onto a piece of paper with a
magnet underneath. The filings would align along the magnetic field lines.
I figured the filings aligned along lines that indicated the highest field
strength but assumed that magnetic lines of force
also existed between the iron filings and that the field was continuous.
Is a magnetic field actually formed from discrete sources (electron spin
from individual atoms) combined to seem like a continuous field? This
analogy reminds me of a ray of light shining through mist filled air. The
beam of light seems continous but is actually formed from individual
photons.
It makes more sense to me to measure a magnetic flux by the attractive
force it exerts on a standard magnetic material when in contact (in
newtons/cm2 for example).
Does anyone know the history of this definition and if it is literal?
Is there really a technique for measuring "lines" of force? Is so, how is
this feat accomplished?
Thanks in advance to the knowledgable physicist who can answer this
question!
Gus Tombros
P.S. I am not a Physicist. But a curious individual who has pondered this
question since my Physics 101 class (years ago).
Richard Herring
> Gauss is a measurement of a magnetic field strength. 1 gauss = 1 line of
> force per cm2.
Actually it's 1 *maxwell* per cm^2.
The SI unit is the tesla, 10^4 gauss. I tesla = 1 weber per square metre.
And - before you ask - the weber is 1 volt-second. So if the flux through
a circuit is changing by 1 weber per second, it will induce an emf of
1 volt.
> The more lines of force, the stronger the magnetic field or> flux.
> The question I have is this: How on earth can one measure lines of force?
See the definition of the weber: in principle, move a coil through
the flux and see what voltage is induced in it.
> As a kid I remember pouring iron filings onto a piece of paper with a
> magnet underneath. The filings would align along the magnetic field lines.
> I figured the filings aligned along lines that indicated the highest field
> strength but assumed that magnetic lines of force
> also existed between the iron filings and that the field was continuous.
Remember that "lines of force" are simply a pictorial analogy for a
vector field. There's just as much field in the spaces between the lines
in the picture.
> Is a magnetic field actually formed from discrete sources (electron spin
> from individual atoms) combined to seem like a continuous field?
Yes. The fields from the separate sources are linearly superimposed.
> This
> analogy reminds me of a ray of light shining through mist filled air. The
> beam of light seems continous but is actually formed from individual
> photons.
Bad analogy. You are seeing individual water droplets refracting
the light beam, not individual photons.
> It makes more sense to me to measure a magnetic flux by the attractive
> force it exerts on a standard magnetic material when in contact (in
> newtons/cm2 for example).
In fact it's defined by the force it would exert on a tiny magnetic
charge. Such things don't actually exist, but this can be turned into
an equivalent definition involving the torque exerted on a tiny
compass needle. Alternatively, you can measure the force exerted on
a moving electric charge, which will be proportional to the field
strength and its velocity.
> Does anyone know the history of this definition and if it is literal?
> Is there really a technique for measuring "lines" of force? Is so, how is
> this feat accomplished?
See above: measure the voltage induced in a moving loop, the torque
on a magnetic dipole, or the force on a moving electric charge.
> Thanks in advance to the knowledgable physicist who can answer this
> question!
--
Richard Herring | <richard...@gecm.com>