Electron flows

Thread Starter

anthonylauly

Joined Jan 7, 2017
5
Hi, I would like to know if the electron flows from the negative or the positive side of the battery, and can I prove that with a simple circuit ?
 

WBahn

Joined Mar 31, 2012
30,060
Yes, in most circuits electrons flow from a more negative potential to a more positive potential. This can be demonstrated pretty conclusively with many tube-based circuits. With solid state circuits it is much more difficult because the most phenomena can be quite adequately explained by either negative charge carriers flowing from negative to positive or positive charge carriers flowing from positive to negative. However, there are some phenomena for which this is not the case -- one example is the Hall effect. So an experiment based on this phenomena can prove, at least in that device, what the polarity of the actual charge carriers is.
 

crutschow

Joined Mar 14, 2008
34,452
Probably the easiest way is with a vacuum tube.
This can tell us not only the direction of electron flow in a battery but also the charge polarity of an electron.

Current will only flow in one direction in a vacuum tube diode.
That is from the hot filament cathode to the cold plate, and only when the plate is connected to the positive side of the battery and the cathode is connected to the negative side.
Since we know that opposite charges attract, this means that the positive plate must be attracting the charged electrons boiling off the hot cathode and the electrons thus must have a negative charge.
The also means the electrons are flowing from the negative to the positive side of the battery.
 

Elektrishun

Joined Dec 27, 2016
58
Does anything really flow when it comes to electrons/current? I read one description that suggested it's a bunch of vibrating particles that don't travel anywhere.
 

WBahn

Joined Mar 31, 2012
30,060
http://www.allaboutcircuits.com/textbook/direct-current/chpt-1/conventional-versus-electron-flow/

When I was in school we used "electron flow" to understand the basics of electrical theory. A few years later when we got into slightly more complex electronic circuitry we used "conventional flow". In the end we were told it didn't matter...sometimes.
Keep in mind that the TS isn't asking about the age old electron-flow vs. conventional flow debate (which is what I expected the thread to be about, too), but rather is it possible to prove that, in non-special case (for lack of a better description) electric circuits is it possible -- and how might you go about it -- to prove that the charge carriers are, in fact, negatively charged and actually move from negative to positive.
 

WBahn

Joined Mar 31, 2012
30,060
Does anything really flow when it comes to electrons/current? I read one description that suggested it's a bunch of vibrating particles that don't travel anywhere.
In AC circuits with no DC component that is largely true, but even then it is a valid question whether the vibrating particles are positive charged or negatively charged. If there is a DC component then there is a net flow of charge carriers, though the velocity is generally quite low. But in many situations that is not the case. Again, vacuum tubes and charged particle beams are obvious examples.
 

crutschow

Joined Mar 14, 2008
34,452
Yes, the velocity of an electron in a wire for typical current levels in pretty slow.
For example, for 5Adc flowing in a copper wire with a cross section of 0.5mm², the average velocity of an electron is about 0.735mm/s or 44mm/min.

For 5Aac in that same wire at 60Hz the electron would move about 6μm in a half-cycle, thus the electron does essentially vibrate in place with AC current in a wire.
(Makes you realize how many free electrons there are in a small piece of copper wire.) :eek:
 
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