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### TestTubeGames Explains

Posted: Thu Jan 14, 2016 3:53 pm
Started a new project recently - making YouTube videos explaining science using my games.

The general notion being:
-these games show off really involved science if you know where to look
-not everyone knows where to look

So why not make a video that cuts to the chase? No downloads or tutorial-levels or science background needed to learn some cool nuggets.

I just posted the first one, about Parallel Wires and Relativity. One of my favorite little bits of physics, in fact.

So, what do you think? Was it understandable? Enlightening? What would you want to see a video about?

### Re: TestTubeGames Explains

Posted: Thu Feb 25, 2016 1:15 am
I checked it out; I'm not very far into physics so far (in fact, we're covering this kind of topic right now), but I from watching that, I believe the wires/currents would attract.
What I'm getting from the video is that the same side on each wire would become more negatively charged due to relativity (since current moves), and then would attract because opposite charges are facing each other. Am I correct?

### Re: TestTubeGames Explains

Posted: Fri Feb 26, 2016 4:17 pm
wtg62 wrote:What I'm getting from the video is that the same side on each wire would become more negatively charged due to relativity (since current moves), and then would attract because opposite charges are facing each other. Am I correct?
Not quite -- I drew the positive and negative charges as two rows, one on top of the other. But in reality, they're mixed in together, so there's no 'sides' persay, where one would be closer than the other.

The reason they attract or repel is because of the length contraction... In the example in the video, the line of negative charges was contracted *more* because of relativistic effects. From the Shocktopus's perspective, that unbalanced the charge in the otherwise neutral wire, making it seem like there were more negative charges. Hence the attraction.

To figure out whether a wire would attract or repel, break the problem into pieces...

The second wire would consist of:
a) A bunch of positive charges standing still
b) A bunch of negative charges moving *up*

The positive charges in the second wire (since they're standing still) would feel the same electric force that the Shocktopus would if *he* were standing still. Nothing. The first wire is, after all, neutral.

It's the moving negative charges that will feel a force. As they move up, length contraction will unbalance the charges in the first wire (from the perspective of the negative charges in the second wire). Will a charge moving *up* in the second wire see more positive or more negative charges in the first wire? So will our negative charge attract or repel to that unbalance?

That will give you the answer. Does that make more sense now?

### Re: TestTubeGames Explains

Posted: Fri Feb 26, 2016 11:27 pm
This does make me scratch my head a bit; but I think by the keyword seem (when you talk about more electrons being there) you mean a wire (which is otherwise neutral) acts as if the other wire is more negatively charged (and vice versa), rather than both actually simultaneously having the same charge.

### Re: TestTubeGames Explains

Posted: Fri Mar 04, 2016 3:57 pm
wtg62 wrote:This does make me scratch my head a bit; but I think by the keyword seem (when you talk about more electrons being there) you mean a wire (which is otherwise neutral) acts as if the other wire is more negatively charged (and vice versa), rather than both actually simultaneously having the same charge.
Exactly. Just as two people passing near light speed would say the other one appeared to be squished. It seems like a paradox, until you realize you need to just focus on one reference frame at a time.

So just think about a single moving charge in that second wire. What force would it feel? (Due to symmetry, it won't feel any force from its own wire... just the other one. So it's much the same case as with the Shocktopus).

Hmmm... sounds like I should probably do a follow-up video that takes the question all the way home... going from the case of a single Shocktopus to the case of a whole 'nother wire.