Dipole problem

  • #1

Homework Statement


Griffiths offers this problem: two point dipoles p1 and p2 are given.They are r distance away and they are perpendicular.We are asked to find torue of p1 (about p1's centre) due to p2 and vice versa.
Well, the situation is that I knoe it is =p cross E
even I know the formula for a point dipole pointing in the z direction:
E_dip=(1/(4*pi*epsilon))(p/r^3)[2cos(theta) (r^)+sin (theta) (theta^)
where (r^) and (theta^) are the unit vectors in a polar system coincident with the xyz system.
I can surely find the result for 1 part.Assuming p1 points in the z direction,it can be evaluated.What could be done in the second case?


Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
Dick
Science Advisor
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Both torques are equally easy to compute. Just rotate your coordinate system. But you don't even have to. Their sum is the time rate of change of angular momentum, a conserved quantity. Think Newton's third law.
 
Last edited:
  • #3
You are WRONG.If I rotate the axes,the relative difference of answers will not be visible.
 
  • #4
Dick
Science Advisor
Homework Helper
26,260
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You are WRONG.If I rotate the axes,the relative difference of answers will not be visible.
Really? I have no idea what you mean to say, but I guess you know best.
 

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