Tube theory confusion

[nee]

Help!

"TUBECAD" says: "[a triode] can only conduct current in one direction: from its cathode to its plate [anode]."

Yet the VALVE WIZARD says that on a graph of a tube's static anode characteristics, the y-axis shows anode current, which is "the current flowing from anode to cathode at any time."

Wha-? Which way does the current flow?

Signed, Confused.

[martin manning]

The Valve Wizard is using "conventional flow" notation, where the charge carriers are assumed to be positive, and current flow is from positive to negative. In "electron flow" notation, the actual motion of (negatively charged) electrons is observed, and the flow is from negative to positive. Either scheme may be followed with equal success, as long as it is consistently followed.

MPM

[Sonny ReVerb]

This stuff always gives me a headache...

http://www.autolabscopediagnostics.com/electron.htm

Nice graphic in this one:

http://www.mste.uiuc.edu/murphy/HoleFlow/HoleFlow.html

[gearhead]

Blame Ben Franklin, but he was just guessing:


http://hypertextbook.com/physics/electricity/charge/

Yes folks, the convetional direction of current flow is opposite the flow of electrons.

[tubeswell]

On the other hand if J.J. Thomson & Co had decided that electrons were 'positively' charged when they 'discovered' them, then I guess electrons would be regarded as flowing from +ve to -ve (however that would still have been opposite to what Benjamin Franklin came up with - right?). And then I guess we would be calling the power rail the 'B-' too, and people would be wondering why. (I better stop before this messes any more with my head.)

[nee]

So if I just say "current is flowing between anode and cathode" I'll be OK?!

I just liked the idea of cathode to anode because I can imagine, in the first stage of a preamp, the signal entering at the grid, then exiting at the anode riding on a wave of electrons from the cathode .

That's wrong ain't it? Oh oh. More study coming up...

[mojo2001]

That's wrong ain't it? Oh oh. More study coming up...

That is actually correct. It might help to think of a power supply as an electron sucker, with B+ terminal as the nozzle of the vacuum. Ground is a huge pile of electrons that get sucked through the circuit by this force of attraction.

For some reason, it seems natural to think of B+ as a pressure hose pushing electrons into the circuit but that's not the way it works.

So when you are working on an amp in your bare feet on a wet concrete floor and you touch the + filter cap terminal, you get electrocuted by electrons flowing from ground through your feet into the PSU, not by electrons shooting into your finger from the cap.

[Andy Le Blanc]

Its a common perception that electricity flows from the battery positive.
I've had arguments with some who refuse to believe any other argument.
Current flow is the opposite, from the ground thru the cathode to be emitted
and collect as the space charge, drawn to the plate with a positive gradient.
across the tubes vacuum. The potential(s) of the control grid(s) is the
"valve" that modifies the flow.

[gearhead]

Its a common perception that electricity flows from the battery positive.
I've had arguments with some who refuse to believe any other argument.
Current flow is the opposite, from the ground thru the cathode to be emitted
and collect as the space charge, drawn to the plate with a positive gradient.
across the tubes vacuum. The potential(s) of the control grid(s) is the
"valve" that modifies the flow.

Now, you got to be careful with terminology. ALL texbooks and references cite CURRENT as flowing from positive to negative voltage. It is the movement of Holes, which is just a convenient way of covering up that fact that Bennie and friends didn't get it right wrt what charge moved where. In that your friends are correct.

The flow of the actual agent of energy, the Electrons, actually move in the oposite direction, from ground to cathode to plate, drawn by the positve voltage applied at the plate.

Believe me, I'm an EE, and when I learned this I was floored. They did teach it early on, so all were aware of it, but still makes the whole field kinda funny.

Now if you want to talk other funny stuff, look up the rate of flow of electrons. It's called the "drift current". Wiki and get another surprise. LOL

http://en.wikipedia.org/wiki/Electric_current

[Structo]

Yeah I remember the hole theory when I was in college.
Then it was used more in semiconductor theory but was still hard to wrap the old noggin around.

[Andy Le Blanc]

O boy.... you'd think it was confusing on purpose.

A negative value means that the actual direction of current through that circuit element is opposite that of the chosen reference direction.

perfectly clear

[Ears]

This stuff always gives me a headache...

http://www.autolabscopediagnostics.com/electron.htm

Nice graphic in this one:

http://www.mste.uiuc.edu/murphy/HoleFlow/HoleFlow.html

Poor explanations such as in the first link (where terminology is confused e.g mixing words such as energy/force, or convention/theory) give me headaches too.

[nee]

Okey-dokey, so if the electrons really are being attracted from ground towards the B+, how does the PI on the 5E3 work, with signal being sent to the power tubes from both anode and cathode?

[Ears]

Okey-dokey, so if the electrons really are being attracted from ground towards the B+, how does the PI on the 5E3 work, with signal being sent to the power tubes from both anode and cathode?

It's called Ohm's law, those electrons flow though both the anode and cathode loads.

[gearhead]

Signal from anode and cathode are inverted relative to each other

Read: http://www.300guitars.com/articles/arti ... -inverter/