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Steady Current and Magnetic Field 
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#1
Feb910, 06:35 PM

P: 8

1. The problem statement, all variables and given/known data
Question 3 of http://www.damtp.cam.ac.uk/user/examples/B10b.pdf . 2. Relevant equations [itex]\nabla \times B = \mu_0 J[/itex] 3. The attempt at a solution I know for a cylinder, J (vector) = J (scalar) * k (vector), where unit k is the vector in the zdirection. So [itex]\nabla \times B = (0, 0, \mu_0 J)[/itex], somewhere (not quite sure where this is true in terms of a, b, d). I think I need to find B for the big cylinder, then B for the small cylinder, and combine them somehow? I don't see why the field in between the cylinders is important; we're only interested in B for x² + y² < a². Thanks! 


#2
Feb910, 08:24 PM

P: 1,368

I think you have everything you need to do this problem. Write down explicitly the sum of the two fields, one from +J and one from J, for any point in the current free region of interest. The x dependence should drop out.



#3
Feb910, 08:32 PM

P: 1,368




#4
Feb1010, 05:45 AM

P: 8

Steady Current and Magnetic Field
My notes on a vaguely similar problem claim B = B(r)e_theta 'by symmetry'. Not quite sure why it's e_theta by symmetry. 


#5
Feb1010, 07:17 PM

P: 1,368

If you are still stuck I'll try and add more. 


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