Go Back   Science Forums Biology Forum Molecular Biology Forum Physics Chemistry Forum > General Science Forums > Physics Forum
Register Search Today's Posts Mark Forums Read

Physics Forum Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.


Question on Perpetual Motion of Second Kind

Question on Perpetual Motion of Second Kind - Physics Forum

Question on Perpetual Motion of Second Kind - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.


Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 01-28-2004, 07:55 AM
Ben Peterson
Guest
 
Posts: n/a
Default Question on Perpetual Motion of Second Kind



I made up two designs for perpetual motion machines of the second kind.
That is, one that converts heat from a single isothermal source directly
into useful work, thus lowering the entropy of the universe in violation of
the second law of thermodynamics. I'd REALLY like to know why they don't
work. I've done a little reading into Maxwell's Demon and information
theory lately, but I still can't figure out the answer to these specific
designs.

Here they are: [Only registered users see links. ]

I'd really like to do my physics undergraduate thesis on the topic of
perpetual motion of the second kind this semester, so any answers you may
have would help me a lot. Thanks!

-Ben


Reply With Quote
  #2  
Old 01-28-2004, 10:05 AM
OC
Guest
 
Posts: n/a
Default Question on Perpetual Motion of Second Kind

"Ben Peterson" <[Only registered users see links. ]> wrote in message news:<bv7pjn$lt2$[Only registered users see links. ].umn.edu>...


Machine #1:

The pressure of the gas is constant, so the piston should not move
over macroscopic distances, apart the small fluctuations.
But piston and generator are outside the isothermal bath, so you have
to show us that they are not at a different temperature.
Also, you should provvide an example of useful work in the drawing
(like lifting a weight).

There are examples of extracting work from brownian motion that use
asymmetric systems (like a piston that move only in one direction).

Machine #2:

The mirror has a temperature and emits and absorbs thermal radiation.
So do the two points. I would expect that the thermal radiation from
the mirror affects the blue and red point.
If no work is done to keep the temperatures of the mirror and the
points constant, then the system will end up at equilibrium.
(A mirror that reflects all EM frequencies does not exist.)


OC
Reply With Quote
  #3  
Old 01-28-2004, 12:39 PM
Bernhard Kuemel
Guest
 
Posts: n/a
Default Question on Perpetual Motion of Second Kind



Ben Peterson wrote:

I invented something similar:

[Only registered users see links. ]

If you find some comprehensive explanations why it doesn't work
I'm interested.

Bernhard

--
Webspace; Low end Serverhousing ab 15 e, etc.: [Only registered users see links. ]
Linux Admin/Programmierer: [Only registered users see links. ]

Reply With Quote
  #4  
Old 01-28-2004, 03:43 PM
Gregory L. Hansen
Guest
 
Posts: n/a
Default Question on Perpetual Motion of Second Kind

In article <bv7pjn$lt2$[Only registered users see links. ].umn.edu>,
Ben Peterson <[Only registered users see links. ]> wrote:

In machine #1, you don't even need the piston and generator because there
will be thermal noise anyway. Put an oscilliscope across a resistor and
you can see it. Sensors are often cooled to reduce thermal noise. But
what that also means in your machine is sometimes the generator will act
like a motor and move the piston against incoming molecules. Expect them
to gain as much energy as they lose, and the temperature to remain
constant.

Turning thermal noise into useful work is another matter; diodes have
thermal noise, too. The second law can be violated in microscopic scales,
but a perpetual motion machine that does something is a macroscopic
device.

Machine #2 is quite clever. Thermal radiation from the mirror will go in
every direction, and any blackbody will absorb as well as it emits. But I
can't think of a good reason to kill a transient dT/dt>0.

--
"In any case, don't stress too much--cortisol inhibits muscular
hypertrophy. " -- Eric Dodd
Reply With Quote
  #5  
Old 01-28-2004, 03:46 PM
Franz Heymann
Guest
 
Posts: n/a
Default Question on Perpetual Motion of Second Kind


"Ben Peterson" <[Only registered users see links. ]> wrote in message
news:bv7pjn$lt2$[Only registered users see links. ].umn.edu...
of

Because your "invention" will vioolate the second law of thermodynamics.

Franz


Reply With Quote
  #6  
Old 01-28-2004, 05:12 PM
Uncle Al
Guest
 
Posts: n/a
Default Question on Perpetual Motion of Second Kind

Ben Peterson wrote:
[snip]

You are wrong - unless you can flip an honest coin heads 10^23 times
in a row. A machine does work. it cannot evade the Second Law.

--
Uncle Al
[Only registered users see links. ]
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
Reply With Quote
  #7  
Old 01-28-2004, 07:13 PM
Marvin Margoshes
Guest
 
Posts: n/a
Default Question on Perpetual Motion of Second Kind


"Bernhard Kuemel" <[Only registered users see links. ]> wrote in message
news:4017ad94$[Only registered users see links. ]...
may

Others have mentioned that the machines all violate the second law of
thermodynamics. To put it another way, none of the processes that are to be
used can operate at 100% efficiency.


Reply With Quote
  #8  
Old 01-28-2004, 08:15 PM
bob
Guest
 
Posts: n/a
Default Question on Perpetual Motion of Second Kind

"Franz Heymann" <[Only registered users see links. ]> wrote:

I break the law daily. Not the second law (twice a day I drive faster
than the posted speed limit on this bridge:
[Only registered users see links. ] - the site is kind of humerous) but
what's the difference?

Does anyone know where I can get me a demon like the one Maxwell had?

Thanks!
Reply With Quote
  #9  
Old 01-28-2004, 10:36 PM
Sam Wormley
Guest
 
Posts: n/a
Default Question on Perpetual Motion of Second Kind

Ben Peterson wrote:

Second Law of Thermodynamics
[Only registered users see links. ]

The second law of thermodynamics prohibits the construction of a perpetual
motion machine "of the second kind."
Reply With Quote
  #10  
Old 01-29-2004, 12:22 AM
Uncle Al
Guest
 
Posts: n/a
Default Question on Perpetual Motion of Second Kind

tadchem wrote:

Encyclopedia of Irish Erotic Pottery
Compendium of French Military Triumphs
The Big Book of British Gourmet Cooking
Biographies of Black African Mathematicians
Directory of Mexican Birth Control Clinics

--
Uncle Al
[Only registered users see links. ]
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
Reply With Quote
Reply

Tags
kind , motion , perpetual , question


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
FFiMP: Misconceptions about Special Relativity Jan Gooral Physics Forum 0 05-22-2008 02:53 PM
What is Gravity? sdr@sdrodrian.com Physics Forum 1 01-27-2008 02:53 PM
The Achilles Heel of String Theory. S D Rodrian Physics Forum 7 07-08-2006 02:40 PM
Question on Perpetual Motion of Second Kind Ben Peterson Chemistry Forum 29 02-03-2004 05:59 AM
21st Century Dynamics Donald G. Shead Physics Forum 5 08-14-2003 11:43 PM


All times are GMT. The time now is 01:45 AM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2005 - 2012 Molecular Station | All Rights Reserved
Page generated in 0.20598 seconds with 16 queries