# Two men or two nature?

#### neila9876

People have two concepts for electric current in physic now.
1. charges pass through unit surface in unit time.
2. The Maxwell replaement current.
Nature should be be only one?

#### HallsofIvy

First of all, 'nature' doesn't define "electric current", people do. Secondly, there are many examples in which one concept has several equivalent definitions. There are always different ways of thinking about the same thing!

1 person

#### neila9876

Yes, nature does not define current, men do it. But current is a natural phenominon: it's charge moving..

#### studiot

People have two concepts for electric current in physic now.
1. charges pass through unit surface in unit time.
2. The Maxwell replaement current.
Nature should be be only one?
First off it's Maxwell's 'displacement current' not replacement current.

And yes there are two concepts for electric current because there are two different types of 'current' which occur in different circumstances.
Only one of these can be justifiably called

"movement of charge" as defined by

"charges pass through unit surface in unit time."

This first type of current is called conduction current and actually is 'carried' by moving charges.

In displacement current the charges do not move unless the current is alternating.

1 person

#### neila9876

Oh, yes...it's "displacement". Chen's first language is not English. Haha...
If the capacitor is full charged, no movement of charge any more, the replacement current between the two panels will also be zero. Right?

Last edited:

#### studiot

Oh, yes...it's "replacement". Chen's first language is not English. Haha...
If the capacitor is full charged, no movement of charge any more, the replacement current between the two panels will also be zero. Right?
Why?

Capacitors pass alternating current as displacement current.

What actually happens depends upon the dielectric medium between the plates.

1 person

#### neila9876

Ok, follow what you are talking:
When capacitor pass alternating current, are charges moving in the plates?

#### studiot

Ok, follow what you are talking:
When capacitor pass alternating current, are charges moving in the plates?
are charges moving in the plates?

not in and also not between, but into and out of.

#### neila9876

What's after "into"? It's "in". What's before "out of"? It's "in". What's behind those two concepts of current is the same natural phenominon: charge moving.