Deriving electromagnetic fieldfor point chargeby nos Tags: charge, deriving, electromagnetic, fieldfor, point 

#1
Feb2113, 10:31 AM

P: 32

Hi all,
I was going through the derivation for the electromagnetic field of point charges by Griffith(Introduction to electrodynamics page 437). I'm missing minus sign somewhere: The book says that:[itex]\nabla(\vec{n}\cdot\vec{v})=\vec{a}(\vec{n}\cdot \nabla tr)+\vec{v}\vec{v}(\vec{v}\cdot\nabla tr)\vec{n}\times(\vec{a}\times \nabla tr)+\vec{v}\times (\vec{v}\times \nabla tr)[/itex] Using the rule for triple cross products gives: [itex]\vec{v}+(v^{2}\vec{n}\cdot\vec{a})\nabla tr[/itex] However is should be: [itex]\vec{v}+(v^{2}+\vec{n}\cdot\vec{a})\nabla tr[/itex] I'm sure Im missing something. Thanks 



#2
Feb2113, 11:00 AM

P: 32

oh I've got it. Forgot the minus sign in the triple cross product rule :$



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