E field outside a current carrying wire

Click For Summary

Homework Help Overview

The discussion revolves around finding the electric field outside a resistanceless wire carrying a steady current, as posed in a problem related to the Poynting vector. Participants are exploring the implications of the wire's characteristics on the electric field generated.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Some participants question the assumption of a linear charge density leading to a radial electric field, suggesting that this may not apply in a dynamic scenario. Others raise the possibility of special relativity affecting charge density and inquire about the implications of resistance.

Discussion Status

The discussion is active, with participants exploring different interpretations of the problem and questioning the assumptions made in the textbook. There is no explicit consensus, but various lines of reasoning are being examined.

Contextual Notes

Participants note the specific edition of the textbook being referenced, which may influence the interpretation of the problem. There is mention of potential differences in content between editions, which could affect the understanding of the concepts involved.

conquerer7
Messages
25
Reaction score
0

Homework Statement



One step in one of the problems in my book (involving calculation of the Poynting vector) asks to find the electric field outside a wire. This wire is resistanceless and the current is steady.

Homework Equations



Maxwell's.

The Attempt at a Solution



Stared at it for a while, had no idea how there would possibly be an electric field, solutions manual says the wire creates a radial one proportional to 1/r.
 
Physics news on Phys.org
Hmm. This is a strange question. It seems your book is claiming that there is some linear charge density produced by the current, which then that makes a 1/r radial field. However, the linear charge density assumes a static scenario, which you don't have. Really, the way a wire works is that there is some potential across it V=IR, and the field is the gradient of the voltage (or, alternatively, the field is J/resistivity where J is current density).
 
Would this have anything to do with special relativity? I remember seeing something about length contraction when switching reference frames once, and about how that produced a charge density out of nowhere.

Edit: what if there's a nonzero resistance?
 
which book? :confused:
 
5th edition of HRK's Physics, chapter 38, problem 11.
 

Similar threads

Replies
2
Views
1K
Replies
14
Views
3K
  • · Replies 8 ·
Replies
8
Views
5K
Replies
4
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
8
Views
1K
Replies
14
Views
5K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
4K