# Definiton VS Assumption VS Different Ways

#### neila9876

There might be one concept several equivalent definitions, people might define current according to positive charge or negative charge. That's the case.
"charge pass through unit surface unit time" is the tradtional definition of current. The full name of "Maxwell displacement current" is "Maxwell displacement current assumption". There might be different ways (or say angles) of thinking about the samething, but "charge pass through unit surface unit time" is "able to think about" while "Maxwell displacement current" is "not able to think about" so that "had to assume", IN ORDER TO SOLVE CONTRADICTION.

#### topsquark

Forum Staff
There might be one concept several equivalent definitions, people might define current according to positive charge or negative charge. That's the case.
"charge pass through unit surface unit time" is the tradtional definition of current. The full name of "Maxwell displacement current" is "Maxwell displacement current assumption". There might be different ways (or say angles) of thinking about the samething, but "charge pass through unit surface unit time" is "able to think about" while "Maxwell displacement current" is "not able to think about" so that "had to assume", IN ORDER TO SOLVE CONTRADICTION.
This is the second time someone has mentioned Maxwell's displacment current." (I didn't bother to find the other comment.)

What I don't understand is why this is a big deal? Part of the electric displacment ( $$\displaystyle \vec{D}$$ ) is free charges moving about. (The other part is polarization of the material the electric field is applied to.) This can easily be seen to create a movement of charges through a surface, which is the definiton of current.

So there is no contradiction. Am I missing something?

-Dan

#### neila9876

First, Chen's first language is not English.
I feel that you take the other part of charge pair into consideration and solve the contradiction. And so you are more excellent than "the standard" and even Maxwell. Isn't it a big deal?

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#### topsquark

Forum Staff
First, Chen's first language is not English.
I feel that you take the other part of charge pair into consideration and solve the contradiction. And so you are more excellent than "the standard" and even Maxwell. Isn't it a big deal?
Sorry. I'm still not following you.

What other "part of the charge pair"? We have negative charges (electrons) moving so we have a current. The other way to look at it is to say we have a flow of positive charges (holes) and get the same current. (The flow of positives is in the opposite direction of the negatives.)

I still don't see the contradiction!

We do have an advantage over Maxwell, though. Maxwell didn't know what electrons were (At least not rigorously. He and others certainly knew that a stream of negative charges could be created but Thompson officially discovered electrons near the turn of the century.) That gives us a better idea of how the displacement actually works.

-Dan

#### neila9876

Your are that kind of "genius make himself confused".
It 's Maxwell who saw the contradiction, not you.
The traditional current concept is unilateral (charge move relative to any frame). Your current concept is bilateral (Charge move relative to charge).
Clear?
If you hug the electron and move with it (frame established always on the electron), can you get "the same opposite current"?

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#### studiot

I think your translation program is missing important words.

For example, topsquark quoted polarisation above.

Charge and current are fundamentally different.

Charge is a real property of of real things (matter).

Current is a theoretical model in circuit analysis.

Most currents do not conform to this definition of yours.

"charge pass through unit surface unit time" is the tradtional definition of current.
For instance in conductors it is fundamentally incompatible with the observation

"Charge resides on the outside surface of a body"

Have you studied charge distribution in conductors?

1 person

#### Woody

I (like Studiot) think the translation is getting in the way...

Are you trying to say that:
The current is dependent on the velocity of the electron(s).
However the velocity is relative to the "observers" reference frame.
Thus the current generated by an electron will be dependent on the reference frame from which it is measured.

#### studiot

I (like Studiot) think the translation is getting in the way...

Are you trying to say that:
The current is dependent on the velocity of the electron(s).
However the velocity is relative to the "observers" reference frame.
Thus the current generated by an electron will be dependent on the reference frame from which it is measured.
thanks Woody for trying to help.

I hop you know that this wood (pun intende) be untrue.

1 person

#### neila9876

Woody is very interesting...Why Maxwell had to assume his replacement current?