Why are electrons negative?

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fagricipni
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Why are electrons negative?

Postby fagricipni » Thu Oct 11, 2012 11:45 pm UTC

http://xkcd.com/567/ "explains" that the convention was started by Benjamin Franklin. But I have not seen anyone give any indication that there is any clue as to why Franklin chose the convention that he did. I would imagine at least one thing he tried was weighing things before and after charging to see if this mobile charge has weight, but while it does -- yes, electrons have mass -- the effect is so small that it could have never been detected by Franklin. I don't know what other observations he or his contemporaries might have actually made that led to any conclusions in this matter. What I wonder is if anyone has any clue as to why Franklin decided that the glass gained "charge-fluid" from the silk, or if he just decided be consistent so that his theory could be easily explained, knowing that the future might show that he had it in the wrong direction.

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cyanyoshi
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Re: Why are electrons negative?

Postby cyanyoshi » Fri Oct 12, 2012 3:39 am UTC

From what I can tell, Franklin himself never gave a reason why one should be plus or minus. He just saw them as tentative labels, and probably chose them completely arbitrarily. Maybe in his mind he saw the cloth as rubbing the charge onto the glass for some reason, but that is just speculation. If you are interested, you could read some of Ben Franklin's letters about electricity to see what you can gather from those (don't mind the Conservapedia-esque aesthetic). But the system he used (and that we use) is not the least bit wrong in my opinion. I read an interesting web page about Electricity Misconceptions quite some time ago that addressed the idea that electrons should be positively charged.

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Re: Why are electrons negative?

Postby MarvinM » Fri Oct 12, 2012 2:03 pm UTC

Link made my day, I haven't read his stuff in a while. I really like the idea that if electrons were positive it would be easier and you'd have to understand less of the problem, so it would be a bad thing.

Word to the wise though, it strongly reflects his own understanding of the universe and is pretty mind expanding but don't bring it up in an argument. Most people won't get it, much of the language is not very formal and most people in education would not benefit from reading it too early.

"Instead you should think of AC energy as a mysterious invisible flow that comes out of the outlet, runs along the outside of both wires of the lampcord, then it dives into the filament of the light bulb. Your electric company is sending out long "sausages" made of electrical energy. The wires are guiding them, and your appliances are absorbing them."

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AvatarIII
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Re: Why are electrons negative?

Postby AvatarIII » Fri Oct 12, 2012 2:49 pm UTC

cyanyoshi wrote:From what I can tell, Franklin himself never gave a reason why one should be plus or minus. He just saw them as tentative labels, and probably chose them completely arbitrarily. Maybe in his mind he saw the cloth as rubbing the charge onto the glass for some reason, but that is just speculation. If you are interested, you could read some of Ben Franklin's letters about electricity to see what you can gather from those (don't mind the Conservapedia-esque aesthetic). But the system he used (and that we use) is not the least bit wrong in my opinion. I read an interesting web page about Electricity Misconceptions quite some time ago that addressed the idea that electrons should be positively charged.


If this is true, would it make no less sense to label electrical charge as something like "blue and orange" rather than "positive and negative"?

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Xenomortis
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Re: Why are electrons negative?

Postby Xenomortis » Fri Oct 12, 2012 3:02 pm UTC

Positive and Negative captures the notion that the two are opposite in some way, that they can combine to form something with no net charge, and can help with the mathematics.
As for why Franklin himself chose them, I don't know. I haven't read the linked letters yet.
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Tass
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Re: Why are electrons negative?

Postby Tass » Fri Oct 12, 2012 5:12 pm UTC

Xenomortis wrote:Positive and Negative captures the notion that the two are opposite in some way, that they can combine to form something with no net charge, and can help with the mathematics.
As for why Franklin himself chose them, I don't know. I haven't read the linked letters yet.


Whereas with color charge there is three "opposite" charges, and here color is strangely appropriate. There is not an orange charge though.

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Re: Why are electrons negative?

Postby Technical Ben » Fri Oct 12, 2012 5:15 pm UTC

AvatarIII wrote:
cyanyoshi wrote:From what I can tell, Franklin himself never gave a reason why one should be plus or minus. He just saw them as tentative labels, and probably chose them completely arbitrarily. Maybe in his mind he saw the cloth as rubbing the charge onto the glass for some reason, but that is just speculation. If you are interested, you could read some of Ben Franklin's letters about electricity to see what you can gather from those (don't mind the Conservapedia-esque aesthetic). But the system he used (and that we use) is not the least bit wrong in my opinion. I read an interesting web page about Electricity Misconceptions quite some time ago that addressed the idea that electrons should be positively charged.


If this is true, would it make no less sense to label electrical charge as something like "blue and orange" rather than "positive and negative"?


Perhaps we need "left and right" then? As in the same with spin. This also allows for the 2 to cancel out without a mix up over the "positive/negative" bit? Even "left and right" spin is a misnomer for particles though.
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Re: Why are electrons negative?

Postby screen317 » Fri Oct 12, 2012 5:22 pm UTC

What is easier to understand if electrons are "positively" charged?

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Xenomortis
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Re: Why are electrons negative?

Postby Xenomortis » Fri Oct 12, 2012 5:34 pm UTC

Tass wrote:
Xenomortis wrote:Positive and Negative captures the notion that the two are opposite in some way, that they can combine to form something with no net charge, and can help with the mathematics.
As for why Franklin himself chose them, I don't know. I haven't read the linked letters yet.


Whereas with color charge there is three "opposite" charges, and here color is strangely appropriate. There is not an orange charge though.


How are there three forms of electrical charge?
We have colour "charge" for where we need more than two options.
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Re: Why are electrons negative?

Postby Xanthir » Fri Oct 12, 2012 8:22 pm UTC

Tass is talking about "color charge", which is something that quarks have. For quarks, the color analogy works out, because stable quark assemblies don't have group color - they're either colorless (two particles with red and anti-red charge, for example), or white (three particles, one each of red, blue, and green charge).
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Xenomortis
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Re: Why are electrons negative?

Postby Xenomortis » Fri Oct 12, 2012 9:34 pm UTC

I interpreted his post incorrectly! I thought he was questioning my post instead of adding to it.

Xanthir wrote:or white (three particles, one each of red, blue, and green charge).

Or anti-quarks with colours anti-red, anti-blue and anti-green (which could be associated with colours cyan, yellow and purple, conveniently keeping with the analogy).
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oxoiron
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Re: Why are electrons negative?

Postby oxoiron » Mon Oct 15, 2012 7:16 pm UTC

screen317 wrote:What is easier to understand if electrons are "positively" charged?
By convention, electrical current flows from higher (positive) potential to lower (negative) potential. The particles actually carrying the charge (electrons) flow in the opposite direction. If electrons were considered to be positively charged, then current and particles would both flow in the same direction, from positive to negative.
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thoughtfully
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Re: Why are electrons negative?

Postby thoughtfully » Tue Oct 16, 2012 5:40 am UTC

And this is also the convention used for other potentials, such as gravity, so it wasn't arbitrarily chosen when applied to electricity.
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oxoiron
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Re: Why are electrons negative?

Postby oxoiron » Tue Oct 16, 2012 8:11 pm UTC

Yeah. Too bad the naming convention for electricity turned out to be "backwards". It's not like anyone back then had any way of measuring which way the charged particles were moving, so the naming could have been opposite to what it ended up and nobody at the time would have known the difference and we would've ended with a convention wherein current and electrons both conveniently flow in the same direction.
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idobox
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Re: Why are electrons negative?

Postby idobox » Thu Oct 18, 2012 12:47 pm UTC

The use of positive and negative makes total sense in electrodynamics, because if you represent charge by a number that can be either positive or negative, the maths work well.
Left/ right, up/down, and other binary systems work not to bad in quantum physics, but very often electric charges are used in macroscopic systems. Also, this positive/negative system is used for spin and other properties, and you use +1/2 and -1/2 rather than up and down in equations.
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