Calculating Current Through a Cylindrical Conductor

  • Thread starter Thread starter DODGEVIPER13
  • Start date Start date
  • Tags Tags
    Conductor Current
Click For Summary

Discussion Overview

The discussion focuses on calculating the current through a cylindrical conductor given a specific current density function. Participants explore the integration process required to find the total current, considering the geometry of the conductor and the appropriate coordinate system for integration.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant states the current density in the cylindrical conductor is given by J=10e^-(1-ρ/a)Uz and seeks to find the current through the cross-section.
  • Another participant suggests integrating the flow normal to the cross-section through which the current is flowing.
  • A question arises about the direction of integration, with one participant asking if it should be along the x or y direction.
  • Clarification is provided that the normal vector is perpendicular to the surface, which is confirmed by another participant.
  • Further discussion indicates that the current flows along the axis Uz, making it perpendicular to the cross-section formed by the x-y plane.
  • One participant proposes switching to cylindrical coordinates for the integration to simplify the process.
  • A mathematical expression for the integration is introduced, suggesting that the differential area element in cylindrical coordinates is dS=ρd(phi)dρ.

Areas of Agreement / Disagreement

Participants generally agree on the need to integrate the current density across the cross-section of the conductor, but there are varying opinions on the specifics of the integration setup and the coordinate system to use.

Contextual Notes

There are unresolved questions regarding the limits of integration and the exact setup for the integration process, as well as the interpretation of the normal vector in this context.

DODGEVIPER13
Messages
668
Reaction score
0

Homework Statement


The current density in a cylindrical conductor of radius a placed along the z-axis is J=10e^-(1-ρ/a)Uz
Find the current through the cross-section of the conductor.

Homework Equations


I=JA
A=(pi)a^2

The Attempt at a Solution


So far I have this I=10e^-(1-ρ/a)Uz((pi)a^2) which I assume I am to integrate but what should I integrate with respect too and what should the limits be I am guessing from 0 to a?
 
Physics news on Phys.org
You integrate the flow normal to the cross section through which it is flowing.
 
So that would be along the x or y?
 
The normal is the perpendicular vector right?
 
Yes, the normal is perpendicular to the surface.
 
ok so a normal vector equals to Uz/Uz (where the bottom Uz is the length of Uz it is in between those two absolute value mark things). Do you have any more hints on how to set this up
 
Your problem states that the current is flowing along the axis Uz, hence it is perpendicular to the cross section formed by the x-y plane.

So you just have to integrate the density given as it crosses the circle of radius a defined by the cylinder of the wire. Since the axis passes along the center of the wire it would be easiest to switch to cylindrical coordinates for this integration.
 
∫JdS=Ienc where dS=ρd(phi)dρ in cylindrical right?
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 9 ·
Replies
9
Views
4K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
4
Views
2K