Energy flux vector field problem is the isotherms are circles

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SUMMARY

The discussion centers on proving that the energy flux vector field, represented by the equation J = -k (del)T, points either toward or away from the origin when isotherms are concentric spheres centered at the origin. The key insight is that the gradient of temperature, -(del)T, is perpendicular to the isotherm surfaces, which are constant temperature surfaces. This geometric relationship establishes that the energy flux vector field must be radial, confirming its directionality relative to the origin.

PREREQUISITES
  • Understanding of vector fields and their properties
  • Familiarity with thermodynamics concepts, specifically isotherms
  • Knowledge of gradient operations in multivariable calculus
  • Proficiency in using the equation J = -k (del)T
NEXT STEPS
  • Study the properties of gradient fields in vector calculus
  • Explore the implications of spherical coordinates in thermodynamic systems
  • Learn about the physical interpretation of energy flux in thermodynamics
  • Investigate the derivation and applications of Fourier's law of heat conduction
USEFUL FOR

Students in physics or engineering, particularly those studying thermodynamics, vector calculus, or heat transfer principles.

doppelganger007
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Homework Statement


Suppose that the isotherms in a region are all concentric spheres centered at the origin. Prove that the energy flux vector field points either toward or away from the origin.


Homework Equations


J = - k (del)T


The Attempt at a Solution


so I know that -(del)T is perpendicular to the surface T, which is constant, but I'm not really sure how to finish off the proof from there...
 
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You are given that " isotherms in a region are all concentric spheres centered at the origin." Suppose you are at a point (x,y,z) on such a sphere. At what angle does the line from (0,0,0) through (x,y,z) cross the sphere?
 

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