Irrotational and divergenceless?

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SUMMARY

The discussion focuses on demonstrating that the electric field E(r) = -grad V(r) is irrotational, meaning that curl(E) = 0, and that the magnetic field B(r) = grad x A(r) is divergenceless, indicated by grad dot B(r) = 0. The proof involves calculating curl(grad V) and utilizing the property that the divergence of a curl is always zero, which is a fundamental aspect of Maxwell's equations. The discussion emphasizes that if div B = 0, then B can be expressed as the curl of a vector potential A, reinforcing the concept of magnetic vector potential.

PREREQUISITES
  • Understanding of vector calculus, specifically curl and divergence operations.
  • Familiarity with Maxwell's equations and their implications in electromagnetism.
  • Knowledge of electric potential V and magnetic vector potential A.
  • Basic concepts of irrotational fields and divergenceless fields in physics.
NEXT STEPS
  • Study the properties of curl and divergence in vector calculus.
  • Explore Maxwell's equations in detail, focusing on the implications of div B = 0.
  • Learn about the physical significance of electric potential V and magnetic vector potential A.
  • Investigate examples of irrotational and divergenceless fields in electromagnetic theory.
USEFUL FOR

Students and professionals in physics, particularly those specializing in electromagnetism, vector calculus, and theoretical physics. This discussion is beneficial for anyone looking to deepen their understanding of electric and magnetic fields.

jlmac2001
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I'm not really sure what I'm being asked to do with the following questions. Will someone help me?

How can you show that E(r)=-gradV(r) has zero curl an is irrotational, i.e. the quantity (grad x E) =0


How can you show that the magnetic field ,B(r)=grad x A(r), is divergenceless i.e. that the quantity grad dot B(r) =0?
 
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Basically, you just go ahead and do it!

That is, start by assuming that you have V(x,y,z) so that E(r)=-gradV(r)= -Vxi- Vy-Vz and calculate curl(E)= curl(grad V). See what happens!
 
if B=curl A, then div B = div (curl A), the divergence of a curl is always zero. Actually this proof is usually done in the opposite order since the div B=0 is one of Maxwell's equations, valid even for time dependent phenomenon (the old there are no magnetic monopoles theorem). If div B=0 then B can be expressed as the curl of another vector, which gets labeled A and we call it the magentic vector potential.
Hope this helps.
Cheers,
Norm
 

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