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Bridge Full-Wave Rectifier Operation

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siliconsurfer

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Hello everyone,

I'm reading the book Electronic Devices (9th ed) by Floyd and got a bit stuck with Bridge Full-Wave Rectifier Operation.

In the book, on page 55, the figure below is shown, and the text reads:

"The bridge rectifier uses four diodes connected as shown in Figure 2–38. When the input
cycle is positive as in part (a), diodes D 1 and D 2 are forward-biased and conduct current in
the direction shown."

**broken link removed**

Does this make sense, I would have drawn the current in the opposite direction.

How should one think about this?

All comments appreciated.

John
 
Does this make sense,
Yes.

I would have drawn the current in the opposite direction.
So would I.

The book is showing "electron flow", the direction in which the electrons are moving, from negative to positive.

What you and I would draw is "conventional current" flow, from positive to negative.

How should one think about this?
If in doubt, state what you are showing, electron flow or conventional current.

JimB
 
The illustration you posted shows just how idiotic it is to talk about "electron current" in this context.
 
I remember saying "current flow left to right" here and some one jumped me about it. Current is negative so......

LOL
 
Thanks to Ben Franklin, this little bit of congitive dissonance has plagued everyone in electronics for over 200 years. We all know which way electrons really move, and we all talk about it the opposite way, and that's just the way it is.

It does have consequences. The reason domestic analog US telephone lines run between *negative* 48 V and earth ground is because that "conventional flow" idea had not yet caught on when Bell did his thing. He knew electrons moved from the battery - terminal, so that's how he built his phone and we're still stuck with it.

ak
 
We analyze positive power as that which is consumed or dissipated and negative power as a supply to show conservation of power.
But for positive logic understanding in schematics we say current flows from high to low voltage.


The book is subtitled "Electron Flow Version" and he publishes both versions.
Electronic Devices (Conventional Current Version), 9th Edition
 
The reason domestic analog US telephone lines run between *negative* 48 V and earth ground is because that "conventional flow" idea had not yet caught on when Bell did his thing.

Is the US phone system truly like that?, isn't it balanced with no ground as in the UK? - phone polarity here is irrelevant.
 
Balanced, yes, but not floating from earth ground. Tip is at -48 wrt Ring, with both built out by 500-1000 ohms depending on the phone system. The US phone system is not as monolithic as many think. There are something like 2000 phone systems in the US. Many small towns still have gear dating way back. Also, many early all electronic phones did not have bridge recrifiers internally, just a single diode. If tip and ring were reversed in the phone jack, an old phone would work just fine while the electronic one would be dead.

Of course, I did most of my phone fiddling in the 60's and 70's, so things might have changed a bit and I didnt' get the memo. If there is a current or ex telco guy around here, I'd love an update.

ak
 
Last edited:
Of course, I did most of my phone fiddling in the 60's and 70's, so things might have changed a bit and I didnt' get the memo.

I think your mention of 'tip and ring' shows that :p

How many decades ago were jack plugs replaced? - I know the USA did so before the UK (and we did it a LONG time ago).
 
Telephone lines in North America use a negative battery voltage to reduce corrosion.
I knew it and here it is: **broken link removed**
 
Thanks to Ben Franklin, this little bit of congitive dissonance has plagued everyone in electronics for over 200 years. We all know which way electrons really move, and we all talk about it the opposite way, and that's just the way it is.

It does have consequences. The reason domestic analog US telephone lines run between *negative* 48 V and earth ground is because that "conventional flow" idea had not yet caught on when Bell did his thing. He knew electrons moved from the battery - terminal, so that's how he built his phone and we're still stuck with it.

ak

I think you had better take a look at the thread in this forum. https://www.electronicspoint.com/threads/current-flow.274848/

Ratch
 
The reason they used positive analog logic flow direction is very logical.
 
Hello everyone,

I'm reading the book Electronic Devices (9th ed) by Floyd and got a bit stuck with Bridge Full-Wave Rectifier Operation.
Well you simply bought the wrong book. You should buy this one:
Electronic Devices (Conventional Current Version) (9th ed) by Floyd
https://www.amazon.com/Electronic-D...tronic+Devices+(Conventional+Current+Version)

1.PNG
 


We just compared books, I got the wrong version :facepalm:..... thanks for pointing this out. Anyhow, this has been a good learning experience, from current flow to the domestic analog US telephone lines. Thanks everyone for your feedback.
 
North American telephone lines DO NOT have one wire connected directly to ground like that, instead they are "balanced" so the other wire is not an antenna to pickup mains hum and all kinds of other interference.
Both wires of a balanced pair pickup the same interference which they cancel.
 
North American telephone lines DO NOT have one wire connected directly to ground like that, instead they are "balanced" so the other wire is not an antenna to pickup mains hum and all kinds of other interference.

Post #8:
"
Balanced, yes, but not floating from earth ground. Tip is at -48 wrt Ring, with both built out by 500-1000 ohms depending on the phone system.
"

ak
 
Electron flow is backwards from "conventional current flow". Ben Franking screwed up. When you study solid state physics, we talk about "hole" flow when we are referring to conventional current. With electron tubes it sometimes makes sense to think of electrons. In chemistry it also makes sense to think of electrons. Electrons don't really "flow". Think of them as a row of bumping cars that get pushed once in a while by a voltage.

FWIW, a 16 MW power plant has to be mathematically be a minus 16 MW power plant because positive power is dissipated and negative power is generated. So, pick a convention and run with it.

Some things like this were not spelled out to me early in the game. Sometimes you have to use the what really happens.
 
Electron flow is backwards from "conventional current flow". Ben Franking screwed up. When you study solid state physics, we talk about "hole" flow when we are referring to conventional current. With electron tubes it sometimes makes sense to think of electrons. In chemistry it also makes sense to think of electrons. Electrons don't really "flow". Think of them as a row of bumping cars that get pushed once in a while by a voltage.

FWIW, a 16 MW power plant has to be mathematically be a minus 16 MW power plant because positive power is dissipated and negative power is generated. So, pick a convention and run with it.

Some things like this were not spelled out to me early in the game. Sometimes you have to use the what really happens.

I think you should look at post #11 in this thread. It shows that "Ben Franking" did not screw up. When calculating currents, it is poor methodology to worry about which direction the charge carriers are moving. Always use the mathematical convention first, and then if you need to know the true direction of the charge carriers, keep the calculated direction for the positive carriers and reverse it for the negative ones. Electrons and holes do flow, otherwise they would not travel anywhere. In a wire, the flow by substitutive displacement like marbles in a hose, not by individual flow like an electron beam in a CRT. There is no mechanical bumping or physical touching, and the attraction by the electric field caused by the voltage difference is constant. In chemistry, both electrons and ions are of interest.

Ratch
 
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