Integration of a solenoidal vector field over a volume

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SUMMARY

The discussion centers on proving that the integral of the solenoidal vector field \( \vec{J} \) over a volume \( V \) is zero, given the conditions \( \text{div}(\vec{J}) = 0 \) within \( V \) and \( \vec{J} \cdot \vec{n} = 0 \) on the surface \( S \) enclosing \( V \). The divergence theorem is initially considered but does not yield a straightforward solution. A breakthrough occurs when applying the divergence theorem to the vector field \( \lambda \vec{J} \) with \( \lambda \) chosen such that \( \vec{\nabla} \lambda \) is a constant vector, leading to a successful resolution of the problem.

PREREQUISITES
  • Understanding of vector calculus, specifically the divergence theorem.
  • Familiarity with solenoidal vector fields and their properties.
  • Knowledge of normal vectors and their role in surface integrals.
  • Basic proficiency in manipulating vector fields and scalar functions.
NEXT STEPS
  • Study the divergence theorem in detail, focusing on its applications in vector calculus.
  • Explore solenoidal vector fields and their implications in physics and engineering.
  • Learn about scalar fields and their gradients, particularly in the context of vector field manipulation.
  • Investigate examples of applying the divergence theorem to various vector fields for practical understanding.
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Students and professionals in mathematics, physics, and engineering who are dealing with vector calculus, particularly those focused on fluid dynamics and electromagnetism.

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Homework Statement



div(J)=0 in volume V, and J.n=0 on surface S enclosing V, where n is the normal vector to the surface.

Show that the integral over V of J dV is zero.



Homework Equations




The Attempt at a Solution



I can't get anywhere with it! The divergence theorem doesn't seem to help, as I just go round in circles. Any help at all will really be useful.

Thanks
 
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Try applying the divergence theorem to the vector field \lambda\vec{J} What happens if you choose \lambda such that \vec{\nabla}\lambda is a constant vector?
 
Thanks for that - everything now works.
 

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