Definition of electric current

Click For Summary

Discussion Overview

The discussion revolves around the definition of electric current, specifically addressing the relationship between charge flow and the rate of change of charge. It explores theoretical and conceptual aspects of current in the context of steady flow in conductors.

Discussion Character

  • Conceptual clarification, Debate/contested

Main Points Raised

  • One participant expresses confusion about the definition of electric current, questioning how a steady flow of electrons can coexist with a zero rate of change of charge (dQ/dt=0).
  • Another participant uses an analogy of soldiers marching to illustrate the concept of steady flow, suggesting that current can be steady even if the rate of charge change is not considered.
  • A third participant supports the idea that current is defined by the movement of charge, indicating that the initial participant's reasoning resembles a divergence of charge rather than the definition of current.
  • Another reply clarifies that the initial analysis pertains to current density rather than current itself, asserting that while current density may not change, the current remains non-zero.
  • One participant provides a numerical example to illustrate that current is the amount of charge passing through a cross-section in unit time, reinforcing the definition of current.

Areas of Agreement / Disagreement

Participants do not reach a consensus, as there are differing interpretations of the definition of electric current and its relationship to charge flow. Some participants argue for a more nuanced understanding of current versus current density.

Contextual Notes

The discussion highlights potential ambiguities in the definitions of current and current density, as well as the assumptions underlying the interpretation of steady flow in electrical contexts.

aalnaif
Messages
6
Reaction score
0
I'm confused by the definition of electric current. It is commonly defined as the time rate of change of charge (I=dQ/dt). However, considering a wire with a steady flow of electrons (a constant, non-zero current), wouldn't the number of charges entering a certain section of the wire equal the number of charges exiting from the other side of the section, such that dQ/dt=0?
 
Physics news on Phys.org
Suppose a general watching the troops saw 10 soldiers per second marching past.

This is and example of steady flow.

So he tells them to speed up and now 100 soldiers per second march past.

Again this is steady flow.

Flow of charge(s) is just like this.
 
Studiot is correct. Current is defined by the movement of charge. You are computing a difference which is more like the divergence of charge.
 
@aalnaif

Just to expand a bit on the answers others have given, what you described in your post would be a current density (i.e. current per unit area or volume), as opposed to the current. Your analysis is correct in that the current density in your example is not changing, however the current is clearly non-zero, as you yourself stated in the example.
 
see it is amount of charge passing through the given cross section in unit time . so if 10 C charge pases in i sec. then I= 10 A
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
998
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 9 ·
Replies
9
Views
4K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 6 ·
Replies
6
Views
1K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K