Maximum voltage on coaxial cable?

Click For Summary

Discussion Overview

The discussion revolves around determining the maximum voltage that a coaxial cable can handle given specific parameters, including the maximum electric field, inner and outer radii, and the nature of the dielectric filling. The scope includes theoretical analysis and mathematical reasoning related to electrical engineering concepts.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • Participants discuss the maximum voltage that a coaxial cable can handle, given a maximum electric field of E=3MV/m and specific dimensions for the inner and outer radii.
  • Some participants express uncertainty regarding the dielectric constant, which is necessary for calculating the maximum charge (Qmax) and voltage (U).
  • There is a suggestion that the breakdown voltage depends on the dielectric's properties and the spacing between conductors, implying a need for additional information.
  • One participant questions the clarity of the problem statement, particularly the description of the dielectric filling and its implications for the electric field being the same in both regions.
  • Another participant notes that the outer radius being a multiple of the inner radius was initially confusing but acknowledges it as part of the problem's parameters.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the interpretation of the problem statement or the implications of the dielectric properties. Multiple competing views remain regarding the necessary parameters for solving the problem.

Contextual Notes

Limitations include the lack of information on the dielectric constant and potential ambiguities in the problem statement, particularly regarding the filling of the coaxial cable and its effect on the electric field.

cdummie
Messages
147
Reaction score
5

Homework Statement


How to determine maximum voltage that coaxial cable, whose height is L and is filled with dielectric in such way that E is the same in the dielectric and in the part of the cable that isn't filled with dielectric (only vacuum),can handle if i have maximum electric field that is E=3MV/m, and i have inner radius a=2cm and outer b=2.72a. Dielectric is homogeneous and linear.

Homework Equations

The Attempt at a Solution


I tried like this U=∫E*dl but since i know exact value of Emax and no data for εr and Qmax i can't solve this.
 
Physics news on Phys.org
cdummie said:

Homework Statement


How to determine maximum voltage that coaxial cable, whose height is L and is filled with dielectric in such way that E is the same in the dielectric and in the part of the cable that isn't filled with dielectric (only vacuum),can handle if i have maximum electric field that is E=3MV/m, and i have inner radius a=2cm and outer b=2.72a. Dielectric is homogeneous and linear.

Homework Equations

The Attempt at a Solution


I tried like this U=∫E*dl but since i know exact value of Emax and no data for εr and Qmax i can't solve this.

The part I bolded looks like a typo -- is it?

The breakdown voltage will depend on the breakdown voltage of the dielectric and the spacing between the conductors. If you have the maximum electric field and the separation (and the dielectric constant), you should be able to calculate the breakdown voltage.
 
Last edited:
berkeman said:
The part I bolded looks like a typo -- is it?

The breakdown voltage will depend on the breakdown voltage of the dielectric and the spacing between the conductors. If you have the maximum electric field and the separation (and the dielectric constant), you should be able to calculate the breakdown voltage.

I don't know what you mean, bolded part is correct b=2.72a, that's the given value. I don't have the value for the dielectric constant, if i had i could easily find Qmax and then find U using E expressed with Qmax. The problem is that i don't have dielectric constant.
 
cdummie said:
I don't know what you mean, bolded part is correct b=2.72a, that's the given value. I don't have the value for the dielectric constant, if i had i could easily find Qmax and then find U using E expressed with Qmax. The problem is that i don't have dielectric constant.

Oh, I see now. The outer radius is given as a multiple of the inner radius -- that's what was confusing me about the dimensions.

The rest of the question is a bit confusing as well. Is there a figure that you can post? What does it mean when it seems to say

cdummie said:
and is filled with dielectric in such way that E is the same in the dielectric and in the part of the cable that isn't filled with dielectric

That makes no sense unless the dielectric constant is the same as free space. Is the problem copied word-for-word?
 
berkeman said:
Oh, I see now. The outer radius is given as a multiple of the inner radius -- that's what was confusing me about the dimensions.

The rest of the question is a bit confusing as well. Is there a figure that you can post? What does it mean when it seems to say
That makes no sense unless the dielectric constant is the same as free space. Is the problem copied word-for-word?
It's not completely filled with dielectric, it's filled with dielectric to the some point and rest is free-space.
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 16 ·
Replies
16
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 7 ·
Replies
7
Views
4K
Replies
10
Views
3K
  • · Replies 9 ·
Replies
9
Views
5K
  • · Replies 8 ·
Replies
8
Views
6K
  • · Replies 1 ·
Replies
1
Views
2K