All About Circuits Forum  

Go Back   All About Circuits Forum > Electronics Forums > Electronics Resources

Notices

Electronics Resources Get help with all types of electronics resources, including books, websites, datasheets, technical literature, and software.

Reply   Post New Thread
 
Thread Tools Display Modes
  #1  
Old 03-08-2013, 12:02 AM
Jsw123 Jsw123 is offline
Junior Member
 
Join Date: Jun 2009
Location: Virginia, USA GMT -4 dst
Posts: 40
Default Electron Flow versus Current Flow

Today, while reading some information about batteries, I ran across an article that described that while electron current flow was negative to positive, conventional current flow is positive to negative. I have always understood that current flow is negative to positive.

In my search for clarity, I found many articles, such as the one in the link below, which suggest that "conventional current flow" is based off some misconceptions from the time in history that scientists believed electricity was a fluid. This suggests to me there is no actual physical difference between electron current flow and conventional current and there is no scientific reasoning to explain the two types of current flow because conventional current flow is a theory that is actually proven wrong.

Am I correct on this?

If so, for electrical components in DC circuitry that may be marked with current direction, rather than marked positive and negative markings (I am thinking of the schematic of a diode for an example), is this flow marking based on electron or conventional current flow?

Link showing electron vs conventional current flows:

http://web.engr.oregonstate.edu/~tra..._vs_conv_I.pdf
Reply With Quote
  #2  
Old 03-08-2013, 01:58 AM
wmodavis wmodavis is offline
Senior Member
 
Join Date: Oct 2010
Location: Colorado, USA
Posts: 578
Default

It is an interesting theoretical discussion for some people but IMO of no practical significance. Using either you can do circuit mesh and node analysis. It is more important to concentrate on other things if your goal is to be a good technician or engineer. Therefore my sugestion is to pick one and consistently use it and focus on learning about controlling the current flow to do useful things. The arrows on some components, rightly or wrongly point in the direction of conventional current so If I were you I'd learn to work with that rather then electron flow. But it's your choice. They both are useful.
Reply With Quote
  #3  
Old 03-08-2013, 02:48 AM
Jsw123 Jsw123 is offline
Junior Member
 
Join Date: Jun 2009
Location: Virginia, USA GMT -4 dst
Posts: 40
Default

So, to confirm, will current flow (and not be blocked by the diode) in the attached diagram, since arrows on devices indicate conventional current flow?

My previous knowledge would lead me to believe current in this circuit would be blocked, but if all symbols use conventional flow rather than actual flow, that would not be the case.
Attached Images
File Type: png Circuit.png (15.3 KB, 27 views)
Reply With Quote
  #4  
Old 03-08-2013, 03:00 AM
wmodavis wmodavis is offline
Senior Member
 
Join Date: Oct 2010
Location: Colorado, USA
Posts: 578
Default

Blocked.
For current to flow the battery + must be connected to the anode of the diode. The arrow of the diode symbol indicates the direction of conventional current flow. + voltage to anode forward biases the diode allowing current flow in direction of arrow or electron flow opposite direction.
Reply With Quote
  #5  
Old 03-08-2013, 03:09 AM
Jsw123 Jsw123 is offline
Junior Member
 
Join Date: Jun 2009
Location: Virginia, USA GMT -4 dst
Posts: 40
Default

Thanks for the clarity. My training on reading the diode symbol (coming from a book called "Electricity 1-7") taught me to read the diode symbol showing that if current was flowing in the direction of the arrow, it would be blocked. I was taught that was what the solid line in front of the point of the arrow was supposed to communicate.

Is this conventional current rule applicable for transistors as well?
Reply With Quote
  #6  
Old 03-08-2013, 03:57 AM
MrChips's Avatar
MrChips MrChips is offline
Super Moderator
 
Join Date: Oct 2009
Posts: 9,315
Blog Entries: 24
Default

It depends on where you first got your training in electricity and electronics.
I was always taught conventional current flow and that works fine for me because it matches the symbols in circuit diagrams.
__________________
Most computer problems can be attributed to a simple problem - a loosewire behind the keyboard.

Reply With Quote
  #7  
Old 03-08-2013, 05:32 AM
WBahn WBahn is offline
Senior Member
 
Join Date: Apr 2012
Location: Larkspur, Colorado
Posts: 8,077
Blog Entries: 9
Default

Quote:
Originally Posted by Jsw123 View Post
Thanks for the clarity. My training on reading the diode symbol (coming from a book called "Electricity 1-7") taught me to read the diode symbol showing that if current was flowing in the direction of the arrow, it would be blocked. I was taught that was what the solid line in front of the point of the arrow was supposed to communicate.

Is this conventional current rule applicable for transistors as well?
The origin of the diode symbol comes from the notion of "cathode rays", which are really electrons. Think of a CRT display -- the CRT is a "cathode ray tube" but we know that the "rays" are really streams of electrons.

The line on the symbol represents the cathode of a vacuum tube and the triangle represents a spray of "cathode rays" coming off of it and going to the other terminal (the anode).

Therefore, with that understanding, you know that for "cathode rays" to flow, the anode has to be more positive than the cathode in order to attrach electrons at the cathode toward the anode.

It is merely a very useful coincidence that the symbolic representation chose to represent cathode rays looks like an arrow pointing in the other direction and, hence, an arrow pointing in the direction of conventional current flow.

As others have said, as long as you are consistent it doesn't matter which you use. There are some situations, particularly when dealing with semiconductor physics or ion beams or such, when it is reasonably important to think in terms of the actual charge carrying "things" that are moving around. But for most circuit analysis you can think of it either way. The reason that conventional current rules the day in engineering is because it allows for a consistent mathematical convention that naturally carries the polarity information through the computations.
Reply With Quote
  #8  
Old 03-08-2013, 01:02 PM
wmodavis wmodavis is offline
Senior Member
 
Join Date: Oct 2010
Location: Colorado, USA
Posts: 578
Default

Quote:
Originally Posted by Jsw123 View Post
Thanks for the clarity. My training on reading the diode symbol (coming from a book called "Electricity 1-7") taught me to read the diode symbol showing that if current was flowing in the direction of the arrow, it would be blocked. I was taught that was what the solid line in front of the point of the arrow was supposed to communicate.

Is this conventional current rule applicable for transistors as well?

I would like to read the exact text in that book (which by the way I taught from in my career) because I believe you simply misinterpreted what it was saying. That is/was a fairly reputable electronics text and that is such a basic electronic component and idea my guess, cuz I do not actually remember that far back, is that is not what it said. I could be wrong but..... show me the text.
Reply With Quote
  #9  
Old 03-08-2013, 03:24 PM
atferrari's Avatar
atferrari atferrari is offline
Senior Member
 
Join Date: Jan 2004
Location: Buenos Aires - Argentina
Posts: 1,545
Default

The aftermath of this, for you, is that when discussing anything related with currents you should make clear what convention you use and be ready for a lot of confusion.

Have you ever tried to drive on the wrong side of a street? Not easy (really not) and even rsiky.
__________________
Agustín Tomás

In theory, there is no difference between theory and practice. In practice, however, there is
Reply With Quote
  #10  
Old 03-08-2013, 09:30 PM
crutschow's Avatar
crutschow crutschow is offline
Senior Member
 
Join Date: Mar 2008
Location: L.A. USA
Posts: 6,556
Blog Entries: 1
Default

Current flow direction was originally designated when they didn't actually know the polarity of the charge carriers and assumed they were positive. When the charge was determined to be negative it was realized that the charge flow was opposite to the assigned current flow.

I like current flow since, with the commonly used positive supply voltage in a circuit, the current flows from the top to the bottom of a typically schematic. Also the current flow in semiconductor components, such as transistors and diodes, is in the direction of the arrow.

The only time you need to really think about electron flow is when looking at semiconductor physics or the inner working of vacuum tubes (valves).
__________________
Zapper
Curmudgeon Elektroniker
Reply With Quote
Reply   Post New Thread

Tags
, , ,


Related Site Pages
Section Title
Worksheet Electron versus Conventional flow
Textbook The Silicon-Controlled Rectifier (SCR) : Thyristors
Video Lecture Electrical Quantities A - Basic Electronics and Units of Measure
Textbook Special-purpose diodes : Diodes And Rectifiers
Textbook Meter check of a diode : Diodes And Rectifiers
Textbook Introduction : Diodes And Rectifiers
Textbook Thyristors : Solid-state Device Theory
Textbook Bipolar junction transistors : Solid-state Device Theory
Textbook The P-N junction : Solid-state Device Theory
Textbook Conventional versus electron flow : Basic Concepts Of Electricity


Similar Threads
Thread Thread Starter Forum Replies Last Post
Ac current flow aamirali General Electronics Chat 8 02-14-2012 11:20 PM
Motivating current versus producing current fullNelson General Electronics Chat 4 01-06-2012 04:32 PM
Looking for help choosing a transistor gte General Electronics Chat 127 06-16-2010 02:29 AM
High voltage extremely low currents Ynot1980 Off-Topic 1 12-16-2009 11:32 PM
voltage dividers pilotnmech Homework Help 16 01-14-2008 02:30 PM

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 08:58 PM.


User-posted content, unless source quoted, is licensed under a Creative Commons Public Domain License.
Powered by vBulletin
Copyright ©2000 - 2014, vBulletin Solutions, Inc.