Main Page | Report Page

 

  Science Forum Index » Physics - Research Forum » would there be a potential devloped across here?...

Author Message
abhilash j pillai...
Posted: Sun Aug 15, 2010 9:04 pm
 
Hello

Consider a straight long tube CD which on conduction electro-
deposition of copper takes place at the cathode (-). The cathode is in
contact with a long piece of wire AB (as shown in the figure -link.)
which is connected to the negative terminal of the battery and the
anode is connected to the positive terminal.
a figure is worth a thousand words - so please use the link below to
view the picture - it greatly helps in proper understanding of the
experiment


http://a.imageshack.us/img7/8676/relativisticexplanation.png

PQ is a rod/wire perpendicular and at the middle of AB. similarly RS
is a rod/wire perpendicular and at the middle of CD. Q and R are
connected by a wire parallel to ABCD arrangement.
Now, ABCD conducts, electrons in RS are attracted towards CD due to
lorentz contraction of moving charges in CD. similarly electrons in PQ
are repelled away from AB. Q and R are connected by a wire parallel
to ABCD.






the question is would there be a potential across PS?

Thanks.
 
abhilash j pillai...
Posted: Mon Aug 16, 2010 9:27 pm
 
Thank you Rich L for trying to answer my question.

As you have noticed, this whole issue (this experiment) is based on one
thing - Lorentz contraction of the moving charges. So let us go to the
simplest case of a metallic wire alone.

when the wire is not conducting, the positive and the negative charge
density are the same. When it conducts, the positive charge density is
the same as that of the above, it dosen't under go any change. But
definitely, there is lorentz contraction of the moving negative charges
and hence there is a greater density of negative charges with respect to
the positive charges. but we know that the wire does not have a net
charge -why?

Thank you.
 
abhilash j pillai...
Posted: Wed Aug 18, 2010 1:06 pm
 
Thank You Rich L
------------------------------------------------------------------------------------------------------------------
---"Because when we do this for real, we maintain the potential of the
[quote]wire, e.g. by connecting it to a power supply.  This results in a very
subtle addition or subtraction of electrons as required to keep the
net charge neutral."
---------------------------------------------------------------------------------------------------------------[/quote]
So, if we consider an isolated circuit like this, a wire is connected
to the two ends of a battery through a thermistor.
intially, this thermistor has a huge resistance (ideal thermistor) and
so no current flows through it and after some time, the temperature of
the thermistor
is varied such that a current strarts to flow in the circuit. So in
this circuit, would not be able to adjust with the effects of lorentz
contraction
with additional addition of charges. So will this circuit show the
effects of lorentz contraction?
 
abhilash j pillai...
Posted: Wed Aug 18, 2010 9:14 pm
 
Moreover, saying that there is a subtle addition or subtraction of
electrons as required to keep the net charge neutral also means that -
an observer in the frame of reference where the conducting electrons
appears stationary, should see a net force on the charge which is
staying at rest with respect to the wire. (without this subtle addition
or subtraction of the charges, for this observer, the force on this
"moving charge" due to lorentz contraction of the positive charges of
the wire is canced by the magnetic force on the charge).

Thank you,
Abhilas J
 
Rich L....
Posted: Thu Aug 19, 2010 9:35 am
 
On Aug 19, 2:14 am, abhilash j pillai <abhilashsidhak... at (no spam) gmail.com>
wrote:
[quote]Moreover, saying that there is a subtle addition or subtraction of
electrons as required to keep the net charge neutral also means that -
an observer in the frame of reference where the conducting electrons
appears stationary, should see a net force on the charge which is
staying at rest with respect to the wire. (without this subtle addition
or subtraction of the charges, for this observer, the force on this
"moving charge" due to lorentz contraction of the positive charges of
the wire is canced by the magnetic force on the charge).

Thank you,
Abhilas J
[/quote]
Actually, it is this change in net charge that is the source of what
we call magnetic forces. Charged particles, in their own rest frame,
do not respond to magnetic fields. They only respond to electrostatic
fields. I could argue that magnetic fields are fictitious much like
Coriolis forces. One of the consequences of special relativity is the
understanding that the Lorentz transform transforms electric and
magnetic fields into each other. This is often not taught to
undergraduates, but electromagnetism makes much more sense once you
understand that the magnetic forces are a relativistic effect. (See
Purcell's book "Electricity and Magnetism"
http://www.amazon.com/Electricity-Magnetism-Berkeley-Physics-Course/dp/0070049084/ref=pd_cp_b_0)
for a very brief version of this see http://physics.weber.edu/schroeder/mrr/MRRtalk.html
..

Rich L.
 
 
Page 1 of 1    
All times are GMT - 5 Hours
The time now is Fri Aug 22, 2014 6:48 pm