Yawp!

[tarigwaemir]

Lowell House, on the Feast of Sts. Nereus and Achilleus

Earlier this afternoon, I spent an hour on an electric potential problem, trying to figure out where in my calculations I lost a factor of two. The problem placed four equal point charges at the corners of a square. I first solved it manually using the formula for electric potential due to point charges (the simplest and most straightforward way). When it didn't correspond to the given answer, I checked my solution by calculator. Then I redid the problem using the definition of potential difference as the line integral of the electric field along the path of motion. Still no luck. I checked my calculus with the calculator, and the answer came out the same. I redrew my diagrams and checked my geometry, just in case. Finally, I went backwards from the solution to try to figure out at which point I lost the factor, and I still couldn't figure out where I went wrong.

An hour! (Admittedly I spent most of the hour staring blankly into space and shuffling through the songs on my iPod.) Then I realized that I forgot to include one of the point charges in the system.

This is why I'm going to fail my physics final.

But no, I've decided to become resolute. I refuse to get another B in a concentration requirement. It's not a matter of GPA or graduate school applications or contagious reading period lunacy anxiety. It's a matter of principle! Physics has been the bane of my life ever since it stopped being straightforward mathematics (i.e. ever since AP Physics), and I am sick and tired of letting it ridicule me like this! No more! I have a backbone! Electromagnetism won't defeat me so easily!

(Anthropomorphizing academic subjects is a symptom of extreme stress.)

Yours &c.

Post-script: Look, shiny new icon I picked up from ashke_icons. Isn't the caption appropriate?

Post-post-script: Yes, there really were saints named Nereus and Achilleus. According to this page they were:

Martyrs of the Roman military. Members of the elite Praetorian Guard, they were reputedly baptized by St. Peter, exiled from Rome with St. Flavia Domitilla, and eventually beheaded.

Comments

[jaebi-lit.livejournal.com]

Oh. So it's not Achilles? :/

[troisroyaumes]

Well, I don't know how accurate the site is, but that's the way they're listed. ::shrugs::

[jaebi-lit.livejournal.com]

It would've been interesting if it were Achilles (Greek) instead of Achilles (Roman soldier). I saw that as your feast day listing and my brain cramped trying to figure out how Achilles (Greek) could be considered a Christian saint.

[troisroyaumes]

Yes, I did a double-take too. The "Nereus" was also odd. I do wonder exactly how accurate this is...I mean, were the Romans in the habit of naming themselves after Greek mythological heroes/demideities? O_O;;

[ladydaera.livejournal.com]

did you do it by summing the potential from each pair of charges? twelve edge pair interactions plus four diagonal pair interactions? that makes for... sixteen potential values to sum up, i think, if i didn't miss anything in my mind's eye...

if this is the question that asks you what happens when you let go of the charges, i remember it. i couldn't solve it either until i asked shaun about it.

good luck...

[troisroyaumes]

No, no, I already figured out my mistake by the time I posted; I was just disgusted because it was such a stupid mistake, and my method of solving the problem was correct (i.e. it led to the correct answer once I fixed my stupid mistake). The problem was easy, but I spent an hour trying to figure out where I went wrong, which was why I was disgusted. It was a square not a cube, so nothing nearly so complicated as what you wrote:

A B
C D

You just had to calculate the potential on A due to the electric field from B, C and D, and what I did was write out the term for D and C, without multiplying the term for C by 2 to also account for B. All that time redoing the problem, and that was where the factor of two had gone missing.

[fadedcliche.livejournal.com]

Just goes to prove, once again, that physics = evil.