Amplifiers, transistors and opamps

[LvW]

But in this case it is electrons moving, not atoms.
What equilibrium is reached that stops the "diffusion" continuing throughout the material?

As I have written in post#43:
This process stops when the force behind this effect equals the force within the E-field caused by the diffusion voltage. Because both forces have opposite directions.an equilibrium does exist (stopping the diffusion process).

 

[meBigGuy]

1. Does the creation of an E field by redistribution of charges result in a momentary magnetic pulse? Can someone calculate its magnitude?
2. Diffusion "pressure" is simply random thermal motion. A certain number of charges have enough thermal energy to cross the barrier, which increases the barrier. That barrier increase is what causes equilibrium.
3. It seems like a net charge flow in one direction would be a current, but it's hard to see thermal motion as a voltage. You can calculate an effective voltage (that's probably the barrier voltage that results) but was there an "applied" voltage?

4. No one has commented on my question about charge redistribution in a battery. When you insert electrodes into an electrolyte, charges move and create a voltage. Was there an "applied voltage" to move the charge?

5. What about moving the plates of a charged capacitor closer together. We have an increased voltage caused by moving charges, but no applied voltage to move them. It was caused by mechanical motion of the plates.

 

[LvW]

I think, your questions concern the DEFINITION of electrical current.
As we can see, charged carriers do not only move because they are exposed to an E-field.
Counter examples: battery (chemical process), pn junction (diffusion pressure),...

For this reason we should remember (or search for) a correct definition for the phenomenon we call "electrical current".
Perhaps it is necessary to add that movement of charges is called "current" only if this movement is caused by an electrical potential difference (resp. a corresponding E-field)?

 

[sophiecentaur]

creation of an E field by redistribution of charges result in a momentary magnetic pulse?

Isn't that basic EM theory? Photons are bound to be emitted whilst the electric energy state inside an object changes. The energy would be very very low of course.

Was there an "applied voltage" to move the charge?

etc
PS this is the kind of "classification" that I have problems with. The situation is the situation and just naming it one way or another doesn't really help. Naming things in this way determines the form of analysis that would be used and, sometimes, there are other, more suitable ways of analysing a situation.
If one chooses to look at a Broadcast Radio transmitter as a source of photons, for instance, the analysis will soon get out of hand. Jeez, the classical approach is hard enough!

 

[meBigGuy]

Photons are bound to be emitted whilst the electric energy state inside an object changes.

Now, that's precise science, yes it is! End of subject. You nailed it. We all fully understand now. NOT!

PS this is the kind of "classification" that I have problems with.

How is my asking if there was an applied voltage to move the charges (when it was diffusion and others are saying there needs to be voltage to cause current) in any way classification?
Do you even understand what is being discussed? Do you think you can make a meaningful contribution rather than useless potshots? (3 of them in that post)

Try presenting some science, physics, or other REAL technical information ,that relates to the thread. Try to stay on topic.

Maybe you could explain specifically how diffusion caused by thermal motion moving charges at the initial formation of a PN junction produces a magnetic moment that emits photons.
Maybe you could explain how moving capacitor plates closer together (charge redistribution) causes emitted photons.
Maybe you could explain how charge initial redistribution in a galvanic cell that is not supplying current causes emitted photons.

Thought not!

 

[sophiecentaur]

Now, that's precise science, yes it is! End of subject. You nailed it. We all fully understand now. NOT!
How is my asking if there was an applied voltage to move the charges (when it was diffusion and others are saying there needs to be voltage to cause current) in any way classification?
Do you even understand what is being discussed? Do you think you can make a meaningful contribution rather than useless potshots? (3 of them in that post)

Try presenting some science, physics, or other REAL technical information ,that relates to the thread. Try to stay on topic.

Maybe you could explain specifically how diffusion caused by thermal motion moving charges at the initial formation of a PN junction produces a magnetic moment that emits photons.
Maybe you could explain how moving capacitor plates closer together (charge redistribution) causes emitted photons.
Maybe you could explain how charge initial redistribution in a galvanic cell that is not supplying current causes emitted photons.

Thought not!

You are making this all far too personal. Please stop.
The fact is that you 'can' if you like, demand to talk in terms of "applied voltage" in any situation and there will be a long winded explanation which sticks to a model involving Volts and that will work. Classifying a problem in inappropriate terms does not help with understanding or with solving the problem, which is the point I was making. Inside the solid state, it is convenient to talk in terms of Energy Levels, Energy Bands and Potentials. Also, charges diffuse when there is a difference in potential in different places. The thermal aspect adds more complication. It's difficult stuff and the course I did was so long ago that I forget the details. My Kittel Solid State Physics book is still on the shelf behind me and I could get better acquainted with it all in time.
I don't actually understand what your "Maybe" comments actually mean.

That is very childish.

 

[Dale]

This thread is closed.