What's the Difference Between Positive and Negative?

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I am aware of what positive and negative polarities are but what specifically causes the distinction between positive and negative polarity?
 

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  • #2
berkeman
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I am aware of what positive and negative polarities are but what specifically causes the distinction between positive and negative polarity?
Welcome to the PF.

What is the context of your question? Polarity of what? Of a capacitor or a resistor, as in electronics? Or as charge on particles?
 
  • #3
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Charge on particles specifically. For example electrons and protons are negative and positive respectively but these are simply names. What is different about a protons positive charge to an electrons negative charge?
 
  • #5
sophiecentaur
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Charge on particles specifically. For example electrons and protons are negative and positive respectively but these are simply names. What is different about a protons positive charge to an electrons negative charge?
There may be a very simple answer to satisfy you.
Early experiments with rubbing glass etc. with fur etc. ( you know the sort of thing) found that some combinations of charged objects attracted and other combinations repelled. The results were looked at and it was concluded that there must be only two kinds of electric charge. They could have been called anything - Red and Blue, George and Harry but the Maths involved when using just 'names' would have made life very hard. It was decided that the charges could best be described by a value (how much charge or how much force etc) and a sign. The choice of which sign to choose for a charged glass rod or a charged piece of amber or from one particular terminal on an early chemical battery was quite (afaik) arbitrary. This was way before they discovered charged sub-atomic particles like electrons and protons. When the electron was discovered and its charge measured, it came out as -1.6021766208(98)×10−19coulombs - and they're all the same.
This negative value of the electronic charge is absolutely fine (really!!!) but it does confuse and upset students because the flow of electricity in metals (and most other things) consists of electrons (negative charges) flowing from the Negative Terminal to the Positive Terminal.
 
  • #6
Averagesupernova
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Welcome to the PF.

What is the context of your question? Polarity of what? Of a capacitor or a resistor, as in electronics? Or as charge on particles?
Hey I can't help but rattle your cage on this. I looked and looked but couldn't find any polarized resistors in my collection. :headbang: LOL
 
  • #7
sophiecentaur
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There's always ONE, isn't there. :H
 
  • #8
berkeman
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couldn't find any polarized resistors
LOL. I meant it in the context of the + and - sides of the resistor that has a DC current flowing through it. :smile:

The question was originally in the New Member Introduction forum, so there was no context at all to try to guess what polarity the OP was asking about. First I moved to EE, and then finally to GP when the OP finally answered with the context.
 
  • #9
Averagesupernova
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You know I am not above learning something. I thought maybe there was something about resistors that I did not know yet. :smile:
 
  • #10
Svein
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The choice of which sign to choose for a charged glass rod or a charged piece of amber or from one particular terminal on an early chemical battery was quite (afaik) arbitrary.
The Greek word for amber is electron...
 
  • #11
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You know I am not above learning something. I thought maybe there was something about resistors that I did not know yet. :smile:
It has too do with current in the circuit the resistor is found in. And the reference point for identifying the polarity is the power source. The end of the resistor that is connected to the negative terminal of the battery is negative when the other end is connected to the positive terminal of the battery.
 
  • #12
sophiecentaur
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The Greek word for amber is electron...
The choice of the sign was long before the electron was found and named. The name was fitted to the fact, in retrospect.
 
  • #13
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It seems the source of electrons was determined and labeled Negative and home was labeled positive. As mentioned previously heating metal in a vacuum produces an electron cloud without anything being connected to it. Putting a piece of metal close to the cloud and connecting the hot plate to the cold plate caused electrons to migrate to the cold plate to return home through the conductor. This caused an electric current in the connecting conductor. Connecting a battery negative terminal to the hot plate and positive to the cold plate enhanced the electron flow. Reversing the connection stopped the flow.
 
  • #14
sophiecentaur
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It seems the source of electrons was determined and labeled Negative and home was labeled positive.
Hang on a bit. They hadn't discovered electrons (and didn't know much at all about Electricity) when the + and - signs were allocated to the batteries that they made. They had no real idea about the Chemistry of how the batteries worked.
Your are post hoc rationalising the situation. If 'they' had decided to call the metal electrode of a Leclanche cell "positive" then it would have turned out that the electron was a positive particle- once it had been found.
 
  • #15
sophiecentaur
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Connecting a battery negative terminal to the hot plate and positive to the cold plate enhanced the electron flow
Also, what they saw was referred to "Cathode Rays" and it was not identified as a stream of particles until even later.
 
  • #16
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Hang on a bit. They hadn't discovered electrons (and didn't know much at all about Electricity) when the + and - signs were allocated to the batteries that they made. They had no real idea about the Chemistry of how the batteries worked.
Your are post hoc rationalising the situation. If 'they' had decided to call the metal electrode of a Leclanche cell "positive" then it would have turned out that the electron was a positive particle- once it had been found.
The "they" was Benjamin Franklin. He was the first to label the poles positive and negative. https://en.wikipedia.org/wiki/Benjamin_Franklin#Electricity

If we ever invent a time machine, Franklin's choice of which pole was negative would be one thing I would love to change. (Just as cosmologists would love to uninvent the phrase "Big bang", and QM physicists would like to choose a different word than observable.)
 
  • #17
sophiecentaur
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Franklin's choice of which pole was negative would be one thing I would love to change.
Yes, on the face of it but having electrons with a negative charge does make people stop and think and it must help to discourage the very Mechanical picture that people risk getting in their heads about Electricity.
I wonder whether any well informed PF Chemists could suggest a better than arbitrary reason for the signs. Could it be anything to do with Adding or Subtracting some element in an electrolytic cell - like you get Hydrogen 'taken out of' water at the (-) Cathode?
Just a whimsical thought but there would have to have been some basis for the choice - if they could have possibly found one.
 
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  • #18
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It seems like arbitrary labeling is based on the triboelectric charge and its behavior relative to objects around it. Imagine working with lightning instead of Amber. A powerful electron spark will leave a small pit on polished graphite if the graphite is positively charged with respect to the source of the spark.
 
  • #19
sophiecentaur
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It seems like arbitrary labeling is based on the triboelectric charge and its behavior relative to objects around it. Imagine working with lightning instead of Amber. A powerful electron spark will leave a small pit on polished graphite if the graphite is positively charged with respect to the source of the spark.
And where would the early workers have got hold of a controllable "powerful electron spark" if they didn't know about electrons? You can't use modern arguments if you want to put yourself in the shoes of ancient Scientists.
 
  • #20
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And where would the early workers have got hold of a controllable "powerful electron spark" if they didn't know about electrons? You can't use modern arguments if you want to put yourself in the shoes of ancient Scientists.
I know that each country's education tends to focus on its own national heroes. But can it be that you never heard of Franklin's kite and key, and Leyden jar Sophie?

Wikipedia said:
In 1750, he [Franklin] published a proposal for an experiment to prove that lightning is electricity by flying a kite in a storm that appeared capable of becoming a lightning storm.
pt1-10.jpg
 
  • #21
sophiecentaur
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I know that each country's education tends to focus on its own national heroes. But can it be that you never heard of Franklin's kite and key, and Leyden jar Sophie?
You are missing my point entirely. Franklin did not know about electrons so how could he have come to any conclusion, based on electrons? He knew nothing of the mechanism of the conduction of electricity by electrons. His lightning source was just a 'black box' for him.
 
  • #22
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And where would the early workers have got hold of a controllable "powerful electron spark" if they didn't know about electrons? You can't use modern arguments if you want to put yourself in the shoes of ancient Scientists.
Lightning was a good source but not controllable so observing electrostatic effects in the dark room or in a nightime lightning strike that "negated" its target must have been fascinating... But what can we tell the op about the difference? The cause of the distinction between them in electricity is a testable fact that allows students and inventors to have standards to work with related to the negatively charged particles that can be easily manipulated to do "work."
I know that each country's education tends to focus on its own national heroes. But can it be that you never heard of Franklin's kite and key, and Leyden jar Sophie?



pt1-10.jpg
There is that burning question about which direction the electrons jump during a lighning strike.
 
  • #23
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You are missing my point entirely. Franklin did not know about electrons so how could he have come to any conclusion, based on electrons? He knew nothing of the mechanism of the conduction of electricity by electrons. His lightning source was just a 'black box' for him.
The lightning thing was a reponse to your question, where did they get a powerful spark?

Franklin didn't need to know about electrons, but he and others did know about charge, and Franklin established the sign convention.

Wikipedia said:
Franklin's discoveries resulted from his investigations of electricity. Franklin proposed that "vitreous" and "resinous" electricity were not different types of "electrical fluid" (as electricity was called then), but the same electrical fluid under different pressures. He was the first to label them as positive and negative respectively, and he was the first to discover the principle of conservation of charge.

I wonder whether any well informed PF Chemists could suggest a better than arbitrary reason for the signs. Could it be anything to do with Adding or Subtracting some element in an electrolytic cell - like you get Hydrogen 'taken out of' water at the (-) Cathode?
The following sounds like something close to the answer to your earlier question.
From, https://www.princeton.edu/ssp/joseph-henry-project/galvanometer/explaining-the-phenomenon/
I found it by searching the term "vitreous" and "resinous"

Fluid Theories
The information presented below is drawn from R.A.R. Tricker's book "Early Electrodynamics: The First Law of Circulation" and "A History of the Theories of Aether and Electricity," by E.T. Whittaker.

rub.bmp.jpg


Du Fay observed that bodies could be electrified in two different ways, depending on the materials used. He classified materials into two groups- "vitreous" and "resinous." Vitreous materials included glass, crystal, gems, hair, and wool, whereas resinous materials included amber, copal (a resin less aged than amber), silk, thread, and paper. The first class when electrified by rubbing was said to have vitreous electricity, whereas objects of the second class would have resinous electricity. Objects that with vitreous electricity repelled each other, but attracted those with resinous electricity. Thus was formed the two-fluid theory of electricity, which stated that electricity was essentially vitreous and resinous fluid which possessed powers of attraction and repulsion.
 
  • #24
sophiecentaur
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The lightning thing was a reponse to your question, where did they get a powerful spark?
You have missed out the operative word "electron" that was in my question. If they didn't know about electrons then they couldn't have knows what they were getting in their lightning strike. (The "two fluid' theory seems to have been in operation at the time). And that is the point I have made several times. Nothing in the history of science could involve the electron until it had been discovered.

I can't see, in your attachment, anything to suggest that the choice of sign was anything other than arbitrary. In fact, the + and - signs on the diagram seem to come from the Historian and not from original work (which seemed to use vitreous and resinous as names for the charges. I really didn't think my views in this thread had been expressed in a particularly confusing way. I was questioning how people without any knowledge of charged elementary particles could possibly have ever used the term "electron" in their discussions of electrical events. When you have read the end of a book, the progress of the plot, half way through may be obvious but it wasn't obvious to the characters in the middle chapters. I am still looking for a logical 'reason' for their choice of sign, other than they flipped a coin. (BTW, I very much doubt that Franklin would have made such a choice all on his own - but it doesn't bother me that he was American :wink:. Some of my best friends are from the US)
 
  • #25
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I can't see, in your attachment, anything to suggest that the choice of sign was anything other than arbitrary.
I'm sorry Sophie. I thought it was implicit that Franklin's choice of polarity was arbitrary. That's why I joked that I would like to have changed that choice if I had a time machine.
 

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