# voltage

Discussion in 'General Electronics Chat' started by peacock paul, Jul 7, 2008.

1. ### peacock paul Thread Starter New Member

Jul 7, 2008
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what would u be expecting to see across the broken points in a broken circuit containing a voltage supply, perhaps an arc not clear on this.

2. ### peacock paul Thread Starter New Member

Jul 7, 2008
9
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its potential energy that can be used if desired , right

3. ### Dave Retired Moderator

Nov 17, 2003
6,960
145

Yes. There will be no arc (certainly not for nominal conditions). If you complete the circuit by closing the break, there will be a current in the circuit.

Dave

4. ### peacock paul Thread Starter New Member

Jul 7, 2008
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thanks dave i am sure there will be more questions but so far fasinating.

5. ### Dave Retired Moderator

Nov 17, 2003
6,960
145
I take it you are reading our e-book (see my signature for links to each volume). If not, you may want to check it out.

Dave

6. ### peacock paul Thread Starter New Member

Jul 7, 2008
9
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in your diagram electron flow notation where there is a diode in place which seems in the wrong direction , wouldn't this open the circuit, if so why is the resistor glowing. should the diode in this diagram be drawn in the other direction.

7. ### Dave Retired Moderator

Nov 17, 2003
6,960
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What diagram?

Dave

8. ### peacock paul Thread Starter New Member

Jul 7, 2008
9
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current shown using electron flow notation in conventional verses electron flow first chapter dc

9. ### Dave Retired Moderator

Nov 17, 2003
6,960
145

In the first figure the left-side of the diode is more positive (as a potential difference) than the right-side - this forward biases the diode - and this is the region where diode conducts as a function of voltage across the diode. In the second figure the left-side of the diode is more negative (as a potential difference) than the right-side - this reverse biases the diode - and in this region the diode does not conduct as a function of the voltage (ignoring reverse saturation currents and avalanche breakdown of the diode).

It is convention that the triangle of the diode when forward biased faces the same direction as the conventional flow of current.

Dave

10. ### peacock paul Thread Starter New Member

Jul 7, 2008
9
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thanks dave have to mull over this awhile and get it into my head. thanks for ur help.

11. ### Dave Retired Moderator

Nov 17, 2003
6,960
145
Don't get too bogged down in the details at this stage, but have a look at the first couple of paragraphs on diodes in this section of the e-book. It should detail the conventional/electron flow conventions with respect to diodes.

Don't worry too much about the latter part of that link which goes into the physics of the diode.

Dave

12. ### Ratch New Member

Mar 20, 2007
1,068
3
peacock paul,

I have seen a lot of folks get really wrapped around the axle on this subject. It comes from trying to designate a current direction based on the actual physical movement of the charge carriers. At first, this seems like a logical sensible thing to do. After all, charge carrier movement is what constitutes current, right? This works OK until you run into situations where charges of different polarities move, such as positive/negative ions in electrochemistry and electrons/holes in semiconductors. Some people blame Franklin for making this mess, saying that he misnamed the charges, but he had nothing to do with it. There were two kinds of movable charges long before he came on the scene. If he called electrons positive, it would solve nothing. Then all the charged carriers now called positive would be negative and still move in a different direction. The so called conventional current designation was implemented by scientists and engineers as a mathematical convention, and designates current direction to be in a positive to negative direction from a voltage source no matter what the polarity of the charge carriers. This agrees with other conventions in physics where higher positive quantities move to lower negative quantities. Diodes are marked according to this mathematical designation. If the real physical direction is required, the charge carrier can be examined and determined on a case by case basis.

Last edited: Jul 7, 2008
13. ### peacock paul Thread Starter New Member

Jul 7, 2008
9
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thanks ratch i will check out the link . still early days for me yet .

14. ### peacock paul Thread Starter New Member

Jul 7, 2008
9
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will check out about diodes thanks dave.

15. ### peacock paul Thread Starter New Member

Jul 7, 2008
9
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Cool got it. diodes point in the direction of conventional flow reguardless ( on a schematic ) .

16. ### Dave Retired Moderator

Nov 17, 2003
6,960
145
Yes - conventional flow through the diode.

Dave