Electric Fields: Charge/Unit Length on Inner Surface of Coaxial Cable

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Homework Help Overview

The discussion revolves around the charge per unit length on the inner surface of a coaxial cable formed by a hollow cylindrical metal tube surrounding a wire with infinite charge. The participants are exploring the theoretical implications of this setup in relation to electric fields and Gauss's law.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are considering the application of Gauss's law and questioning whether to treat the cylinder as absent in their calculations. There is also a discussion about the behavior of charges in a conductor when exposed to an electric field.

Discussion Status

Some participants have provided hints regarding the use of Gauss's law and have raised questions about the assumptions involved in the scenario. There is an acknowledgment that the charge on the inner surface is not zero, and the concept of charge accumulation in conductors is being explored.

Contextual Notes

Participants are navigating the complexities of the problem, including the implications of using a Gaussian surface and the nature of electric fields in conductors. There is an underlying assumption that the wire creates an electric field that influences the charge distribution on the cylindrical surface.

steph124355
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I'm a little stuck on the theory behind this question:

(in relation to a line of infinite charge: a wire)
A hollow cylindrical metal tube with inner radius 2.5mm is now placed around the wire, to form a coaxil cable. What will be the charge per unit length on the inner surface of the tube. Explain.

I am thinking it is 0, how or why i got that I don't know!
 
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Hint: Make use of Gauss's law.
 
Use Gauss' law as though the cylinder is not there?
In which case to calculate using E= λ/(2πε_0 r) and use the 2.5mm as the radial distance?

Is there any different concepts behind this scenario compared to using a gaussian surface?
 
steph124355 said:
(in relation to a line of infinite charge: a wire)

Infinite charge...wow...wonder how that happens
 
Its not 0. Considering that metals are good conductors, what happens is that when placed in an electric field, a polar accumulation of charges occur (meaning the positive charges go in one direction and the negative in the other). Therefore, charges accumulate on the surfaces of the cylinder. The inner surface will have a charge density.
 
haha thanks!
physics does my head in but i enjoy it!
thanks for your help
 

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