Confusion on electrical current vs charge flow

In summary, it has long been the convention to take the direction of electric current as if it were the positive charges which are moving. However, this is not always the case, as is the case with a reversed-biased diode.
  • #1
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it has long been the convention to take the direction of electric current as if it were the positive charges which are moving

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elecur.html#c3

The conduction direction for electrons in the diagram is right to left, and the upward direction represents increasing electron energy.

http://hyperphysics.phy-astr.gsu.edu/hbase/solids/pnjun2.html#c2

(Using the diagram pointed to by the link)

A hole wants to increase it's energy, right? So it should have no problem flowing right to left. Likewise, an electron wants to decrease it's energy so it should have no problem flowing left to right.

So why is there no current flow in the direction of the electric field, right to left? (I almost can't even type that because I can just see that the depletion region is in the way, creating an open of sorts. But I would like to try to understand it from the band diagram point of view.)

Is it that there are no electrons, other than the minority carriers, available to flow in the P-side? (i.e. they are all already in the lowest state.) If this is the case why doesn't the battery act as an electron source? (vice-versa for the holes) Shouldn't electrons at the negative terminal supplied by the battery create a current in the direction opposite to the "conduction direction" of the P-N junction? (i.e. travel from p-side to n-side, "conduction direction" in the diagram is defined as n-side to p-side)

I guess the charge carriers don't flow like that from a battery. But if the load was a resistor, from the first quote the current is in the direction of the positive charge carriers, positive carriers flow in the direction of the electric field, and the electric field points right to left. So maybe it does?

But I know this cannot be correct because this is a reverse biased diode, and I am confident only the leakage (minority current) exists inside a reverse biased diode.

It seems like I almost have to be abusing one of these definitions. But which one?

I found some links on batteries but it seems like it could be either way. Electrons flow from positive terminal (i.e. it's positive because the electrons are gone) or electrons flow into positive terminal (due to electrical field).

I know I am making a mistake in my logic and I feel like this should be so obvious but I am just not getting it. I guess I have mental block or something. :)
 
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  • #2
The lack of conduction due to the depletion zone only applies to a P-N junction without an external voltage applied to it (i.e. equilibrium). Once you forward bias the junction, current can move quite freely.

Claude.
 
  • #3
Can't lack of conduction also apply to a P-N junction with an external field which points from n-side to p-side? This represents a reversed biased diode with a depletion region that has increased its width relative to thermal equilibrium, correct?. It conducts majority carries even less due to the fact that they need even more energy to move across the junction in the conduction direction (from n-side to p-side for electrons).

So, if this thing appling this external field is a battery, then does it have no electrons available on the p-side and no holes on the n-side?
 
  • #4
Not if its reversed biased, no. If the junction is reversed biased, the battery wants to push all the electrons toward the N side and all the holes toward the P side.

Claude.
 

1. What is the difference between electrical current and charge flow?

Electrical current refers to the flow of electric charge, while charge flow specifically refers to the movement of electric charges. In other words, electrical current is the rate at which charge flows through a conductor, while charge flow is the actual movement of the charges themselves.

2. How are electrical current and charge flow related?

Electrical current and charge flow are directly related. An increase in electrical current will result in an increase in charge flow, and a decrease in electrical current will result in a decrease in charge flow. This is because electrical current is a measure of the amount of charge that passes through a point in a circuit per unit time.

3. Can there be electrical current without charge flow?

No, electrical current cannot exist without charge flow. In order for electrical current to exist, there must be a flow of electric charges through a conductor. If there is no movement of charges, there is no electrical current.

4. How is electrical current measured?

Electrical current is measured in units of amperes (A). One ampere is equal to one coulomb of charge passing through a point in a circuit per second. This can be measured using a device called an ammeter.

5. Is electrical current the same as electric power?

No, electrical current and electric power are two different concepts. Electrical current refers to the flow of electric charge, while electric power refers to the rate at which work is done or energy is transferred in an electrical circuit. They are related, as power is equal to the product of current and voltage, but they are not interchangeable terms.

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