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electric current

 
 
Reply Thu 31 Mar, 2016 05:34 am
I always thought that electric current is a flow of electrons. But I am reading a popular textbook (Glencoe's Physics: Principles and Problems, written by Paul Zitzewitz), that illustrates an electric circuit with a generator and a motor and positive charges flowing through the circuit (p. 509). This book is usually very clear, but I find this confusing. Does anyone know how to make sense of this diagram?
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Type: Question • Score: 4 • Views: 777 • Replies: 10
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fresco
 
  2  
Reply Thu 31 Mar, 2016 06:19 am
@Brian DAgostino,
Like water flowing 'downhill', conventional current flows positive to negative which was the concept prior to the discovery of 'the electron', which is negative, and therefore flows the other way. Mathematically it makes no difference to the results of equations, and hypothetical positive charges called 'holes' are often depicted 'flowing' in micro-circuits.
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engineer
 
  1  
Reply Thu 31 Mar, 2016 11:21 am
@Brian DAgostino,
Ben Franklin designated the flow and he got is wrong. Now we all use what he defined by convention.

http://imgs.xkcd.com/comics/urgent_mission.png
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Amoh5
 
  0  
Reply Sun 3 Apr, 2016 07:33 pm
@Brian DAgostino,
Coventional flow is an incorrect out-dated model that came from the use of negative earth, or neutral earth. The pictorial model had the power source positive terminal at the top where the electrons are traveling down to the positive wire of the appliance, traveling down through the negative wire of the appliance, traveling down further to the earth.
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Amoh5
 
  0  
Reply Mon 4 Apr, 2016 06:48 am
@Brian DAgostino,
Obviously the power source negative/neutral terminal is connected to the earth/ground for a return path...
Later on experts found out that current actually flows in the opposite direction from the negative terminal to the appliance then to the positive terminal.
Even though conventional flow is now invalid, some teachers and text books still use conventional flow to explain the operations of semi-conductor components because diode schematic direction arrows point in the conventional flow direction making it easier to explain semi-conductor operations...
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Leadfoot
 
  1  
Reply Mon 4 Apr, 2016 07:15 am
The reality is clearer when you look at cases where 'positive' flow makes no sense. Consider the electron gun in a CRT or current flow in a vacuum tube. The old view simply doesn't work in these cases.
fresco
 
  1  
Reply Mon 4 Apr, 2016 07:58 am
@Leadfoot,
Laughing
Good word that...'reality' !
Try asking a physicist what 'an electron really is'. ....Don't hold your breath !

I continue to be amazed by the lack of depth exhibited on this forum with respect to the understanding of the ontological and epistemological status of scientific models. If the criterion was merely 'making sense' then most of QM would go out of the window !
timur
 
  1  
Reply Mon 4 Apr, 2016 09:09 am
@fresco,
People cannot get past naive realism..
fresco
 
  1  
Reply Mon 4 Apr, 2016 09:25 am
@timur,
Very Happy
0 Replies
 
Leadfoot
 
  1  
Reply Mon 4 Apr, 2016 10:28 am
@fresco,
Quote:
If the criterion was merely 'making sense' then most of QM would go out of the window !
The criterion is not only 'making sense' but making stuff work. If we relied on what we now know of QM instead of classical physics, all the progress in the field of electricity since the 18th century would go 'out of the window'.

QM may be of real use in the future but right now it's only useful for the useless navel gazing that you seem to be enamored of. Good luck with that 'reality' :-)
fresco
 
  1  
Reply Mon 4 Apr, 2016 11:29 am
@Leadfoot,
Agreed ! As far as scientific modelling is concerned ,'what works' takes precedence over 'makes sense'. To think that's 'navel gazing' is somewhat bizarre.
0 Replies
 
 

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