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Superconductors and induced current

A very short summary of super-conductors: they are conductors that provides no resistance to a current flowing through them. Despite the rather simplified explanation, they are an extremely complex study in quantum mechanics and a whole slew of scientific research besides. But for our purposes, the above definition shall suffice.

Now I'll introduce Ohm's law:
V=IR .... (1)
V is voltage, I is current, R is resistance. So, given zero resistance in a super-conductor, one would logically expect therefore, to never measure a voltage across a superconductor, even if you injected an infinite amount of current. On a side note, superconductor have what is called a critical current above which they cease to be superconductors.

And the last equation for the night, is one that gives the electric field (E) induced by a changing magnetic field, (B).
E = -dB/dt ... (2)
Simply put, E is the negative gradient of B over time. Now here is what I am puzzling over:
  1. Let there be a changing B around a superconductor loop
  2. By (2) this would produce an electric field, and thus a voltage, in the superconductor loop
  3. Yet by (1) this is impossible, because anything multiplied by 0 gives 0
What it means if the following:
  1. I have made a mistake somewhere
  2. Ohm's law doesn't hold for superconductors.
Its most likely 1 is true :) Either way, here are more questions

  1. So what does happen when you try place a superconductor in a changing magnetic field?
  2. What would you measure?
Oh, and here is a fractual pi



Close your eyes... relax....

And fade into a world where everything happens at snails pace... WAKE UP!

No idea what that sentence had to do with anything, but today has been a slow day, and enjoyable day. A day when I could come home, and not do *any* uni work.

It was a beautiful day :)

Electromagnetism module in physics finished today, and we start quantum mechanics (lies to children style) tomorrow. Can't wait :)

Before I had off to bed and read Heart of Winter, I would like to bring to your attention a thedailywtf, a site where amazing working production code is displayed for the world to admire. *cough*

Oh, one thing before I leave, do you think a person should be able to legally own an idea?



Rambling thoughts

Poor neglected blog...

On Wednesday was the parade for the Olympians. Pics will hopefully go up *nudges steve*.
NB: I am to blame for bad photography...

A sad thing I noted today, whilst comparing the front pages of The Australian and The Sydney Morning Herald. The only story the two papers had in common was about Sally Robbins getting slapped...just goes to show how objective our media are, eh? The only thing they can agree is front-page news is a story about someone getting bitch-slapped....and that it featured high-profile athletes only adds to the tragedy.

O tempora! O mores!

Other than that...SUSPECTS trip coming up (whoo! 3 day engineering piss-up - and it's educational!). Can't wait for the break...I need a holiday. And it also means I will get a chance to get Linux. :)

May Windows, along with arts degrees, be commended to the dustbin of history....
(Dr. Karl rocks :P)

Another thing I am looking forward to: October 9, the day we get to vote Johnny out. Make that another one for the dustbin...



Tale of a graph

The tale of the graph started like any other: I had some data, and I need it to be plotted, nicely. The data in question is the scalability resport for emma's RSA implementation. One would naturally fall into thinking it would be piece of pie getting it to work... but alas, it was not so. Neither open office nor appleworks would plot this to my satisfaction, and I could not find another suitable tool. In desperation I turned to freshmeat, and behold! ploticus was brought forth to stand trial. Scanning through the concise documentation, the belief this was the one took hold.

After constructing a commandline as mighty as any I have ever constructed, I invoked it through the glory that is bash:
ploticus -prefab lines x=1 y=2 y2=3 data=rsa-scale.txt 

header -png title="RSA implementation scalability"
titledet="align=center" autow=yes
xlbl="Input size (characters)" ylbl="Time taken (ms)"
ygrid=yes name="Time for encryption"
name2="Time for decryption" ylbldet="adjust=-0.1,0"
-pagesize 20,20

In the wake of this spell, a graph sprung forth, and my eyes beheld such beauty the monitored sung in its percuilar high pitched whine (or maybe thats just the high freq filtering caps dying...). I give unto the world, the graph.

Thank god for open source software :)





My sheer stupidity lead my software group to lose 2 marks :S F**king hell. For the unwary, .hashCode() can, and will return negative values. I relied on it not to, even though I should have realised it will, due to the algorithm used. This had the effect of breaking our system based on the strings entered, which was really f**king bad.


Sorry sorry sorry sorry sorry sorry sorry! :(

I will do my best not to make the same stupid f**king mistakes again.