This
page will describe PHYS 213 James Scholar Assignment 2.
First,
complete the following related calculation. Consider a very simple model of a
computer memory, in which molecules are either found to reside in the left half
of their memory cell (encoding a "0"), or in the right half (encoding
a "1"). Imagine that we
have a 10-bit register. Initially
each cell is in the "0" state (i.e., all particles are in the left
side of their respective cells); after the computation, they are in either half
of the cell (depending on the specific computation). This doesn't necessarily
require any work, e.g., if one simply pulls out (transverse to the axis of the
memory) the dividing wall between the "0" and "1" side, the
particles can by free expansion move from the "0" state into the
"1" state.
Your
task is to determine the energy cost to reset the 10-bit register to its
initial state, where every particle is again in the "0" side of its
cell. This can be done by using a
piston to push the particles (~compressing the gas) so that they can only occupy
the left side of the cell.
Here
are the two relevant questions for you to answer:
1.
What is the change in (dimensionless) entropy in this process?
2.
What energy is required to carry out the process?
Then,
read the extremely interesting article SciAmDemons-Bennett,
which links thermodynamics to information theory, and write a 1-2 page essay on
it in which you:
a.
Summarize the problem of Maxwell's demon
b.
Summarize the several incorrect solutions to this paradox
c.
Explain the correct solution
d.
Finally, explain the connection between this topic and that of "reversible
computing" (which you should research a little).
Deposit your paper here by 5pm Friday, April 8, 2010.
View the articles here.