What Is the Optimal Inner Radius to Minimize Electric Field in a Coaxial Cable?

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SUMMARY

The discussion focuses on determining the optimal inner radius (a) of a coaxial cable to minimize the electric field while maintaining a fixed outer radius (b) and a given potential difference (V0). The potential is expressed using Laplace's equation as V(r) = V0 ln(r/b) / ln(a/b). The electric field (E) is derived as the negative gradient of the potential, E = -∇V. The objective is to find the inner radius that yields the largest value of the electric field at its minimum, which involves evaluating the electric field at various points on the conductors' surfaces.

PREREQUISITES
  • Understanding of Laplace's equation and its applications in electrostatics.
  • Knowledge of electric field concepts and the relationship between electric field and potential.
  • Familiarity with calculus, specifically gradient calculations.
  • Basic principles of coaxial cable design and its electrical properties.
NEXT STEPS
  • Study the derivation of electric fields from potentials in cylindrical coordinates.
  • Learn about optimization techniques in calculus to find minimum and maximum values.
  • Explore the implications of coaxial cable dimensions on electric field distribution.
  • Investigate the effects of varying potential differences on electric field strength in coaxial cables.
USEFUL FOR

Students in electrical engineering, physicists studying electrostatics, and professionals involved in coaxial cable design and optimization.

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Homework Statement


If anyone could clarify this statement for me, I'm having a bit of difficulty interpreting what the heck I'm supposed to do:

"For a given potential difference V0 between the inner and outer conductors and for a given fixed value of b, determine the inner radius a for which the largest value of the electric field is a minimum."I found the potential fairly easily using Laplace's equation
V(r) = \frac{V_0 ln(r/b)}{ln(a/b)} (a is inner radius, b is outer)
I know that the electric field is the negative gradient of potential, but I really don't know what they are getting at.
 
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Homework EquationsV(r) = \frac{V_0 ln(r/b)}{ln(a/b)}E=-\nabla VThe Attempt at a SolutionI think what they are looking for is the minimum value of the largest electric field (so the maximum of the minimums). You can use the equation for the electric field to determine the electric field at various points on the surface of the inner and outer conductors. Then, you can compare the values at these points to find the point with the maximum of the minimums. This will give you the inner radius a that produces the largest value of the electric field that is also a minimum.
 

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