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Guest
Posted: Fri Aug 17, 2007 10:34 am
I'm sure this is fairly basic, but I'm a mechanical engineer so bear
with me :p I have been trying to read up on some properties and
Maxwell's equations but its been while since freshman year physics.

I have seen a few demonstrations on how to make a spinning plate
dampen its motion, most of the involve placing a magnet in front of
the plate. My question is what happens if you have a current carrying
coil on either side of the plate, so the B field goes through the
plate perpendicular to the spinning face of the plate, would this
cause the motion of the plate to slow? Can someone explain the vector
forces to me and how the relate to oppose motion of the plate? Thanks
guys.
Guest
Posted: Tue Aug 21, 2007 10:58 am
Similar to this design.. or is this a generator?


<img src="http://physics.kenyon.edu/EarlyApparatus/Electricity/
Unipolar_Generator/kenyon12a.JPG">
Don Kelly
Posted: Tue Aug 21, 2007 10:14 pm
Guest
The site seems to be closed to the general public. From the title it refers
to a homopolar machine- once used as a low voltage, high current DC
generator but as the only difference between a generator and a motor is the
direction of energy flow, it could be used as a motor (generally not
practical).
Consider this: What is the difference between a magnetic field produced by
a permanent magnet and an electromagnet of the same geometry? B fields
don't have labels. It is possible to work out the forces involved as well as
generated voltages using either Coulomb's law (applied twice) or even with
Faraday's Law along with Coulombs law (although some dispute the latter).
--

Don Kelly dhky@shawcross.ca
remove the X to answer
----------------------------
<MattCharos@gmail.com> wrote in message
news:1187711892.290546.277720@e9g2000prf.googlegroups.com...
Quote:
Similar to this design.. or is this a generator?


img src="http://physics.kenyon.edu/EarlyApparatus/Electricity/
Unipolar_Generator/kenyon12a.JPG"
Guest
Posted: Wed Aug 22, 2007 2:44 pm
Thanks for the reply, I guess I cant link pictures on this.. but I was
able to access the website, perhaps that will work

http://physics.kenyon.edu/EarlyApparatus/Electricity/Unipolar_Generator/Unipolar_Generator.html

However, my interest is not in making a motor or generator, but an
eddy current dampening system, similar to the setup pictured on the
above site: basically, have an electromagnet coil on either side of
the plate. It was my (limited) understanding that this would require
either a stationary conductor and a moving B field or in this case,
have the 2 coils generate a constant B field perpendicular to the face
of the plate spinning between them, like this:

N-coil-S ====>B (plate) B====> N-coil-S

or better yet, if they were connected, like in a C-shaped electro-
magnet:


N-coil-S ====>B (plate) B====> N-coil-S
| |
|-----------------------------------------------------------|

With the velocity vector of the plate moving into or out of the
screen. Will this dampen the motion? The only vectors I need to
determine this, as far as I can tell is the current density (J?) and
the resulting Force the eddy currents will have, if any.



On Aug 21, 10:14 pm, "Don Kelly" <d...@shaw.ca> wrote:
Quote:
The site seems to be closed to the general public. From the title it refers
to a homopolar machine- once used as a low voltage, high current DC
generator but as the only difference between a generator and a motor is the
direction of energy flow, it could be used as a motor (generally not
practical).
Consider this: What is the difference between a magnetic field produced by
a permanent magnet and an electromagnet of the same geometry? B fields
don't have labels. It is possible to work out the forces involved as well as
generated voltages using either Coulomb's law (applied twice) or even with
Faraday's Law along with Coulombs law (although some dispute the latter).
--

Don Kelly d...@shawcross.ca
remove the X to answer
----------------------------<MattCha...@gmail.com> wrote in message

news:1187711892.290546.277720@e9g2000prf.googlegroups.com...

Similar to this design.. or is this a generator?

img src="http://physics.kenyon.edu/EarlyApparatus/Electricity/
Unipolar_Generator/kenyon12a.JPG"
Guest
Posted: Wed Aug 22, 2007 2:49 pm
Sorry, looks like the formatting on that text representation might
have been skewed. The C magntet should connect to the South pole of
the the right coil.



On Aug 22, 2:44 pm, MattCha...@gmail.com wrote:
Quote:
Thanks for the reply, I guess I cant link pictures on this.. but I was
able to access the website, perhaps that will work

http://physics.kenyon.edu/EarlyApparatus/Electricity/Unipolar_Generat...

However, my interest is not in making a motor or generator, but an
eddy current dampening system, similar to the setup pictured on the
above site: basically, have an electromagnet coil on either side of
the plate. It was my (limited) understanding that this would require
either a stationary conductor and a moving B field or in this case,
have the 2 coils generate a constant B field perpendicular to the face
of the plate spinning between them, like this:

N-coil-S ====>B (plate) B====> N-coil-S

or better yet, if they were connected, like in a C-shaped electro-
magnet:

N-coil-S ====>B (plate) B====> N-coil-S
| |
|-----------------------------------------------------------|

With the velocity vector of the plate moving into or out of the
screen. Will this dampen the motion? The only vectors I need to
determine this, as far as I can tell is the current density (J?) and
the resulting Force the eddy currents will have, if any.

On Aug 21, 10:14 pm, "Don Kelly" <d...@shaw.ca> wrote:

The site seems to be closed to the general public. From the title it refers
to a homopolar machine- once used as a low voltage, high current DC
generator but as the only difference between a generator and a motor is the
direction of energy flow, it could be used as a motor (generally not
practical).
Consider this: What is the difference between a magnetic field produced by
a permanent magnet and an electromagnet of the same geometry? B fields
don't have labels. It is possible to work out the forces involved as well as
generated voltages using either Coulomb's law (applied twice) or even with
Faraday's Law along with Coulombs law (although some dispute the latter).
--

Don Kelly d...@shawcross.ca
remove the X to answer
----------------------------<MattCha...@gmail.com> wrote in message

news:1187711892.290546.277720@e9g2000prf.googlegroups.com...

Similar to this design.. or is this a generator?

img src="http://physics.kenyon.edu/EarlyApparatus/Electricity/
Unipolar_Generator/kenyon12a.JPG"
 
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