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Renaldo
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Homework Statement
A current of constant density, J0, flows through a very long cylindrical conducting shell with inner radius a and outer radius b. What is the magnetic field in the regions r < a, a < r < b, and r > b? (Use any variable or symbol stated above along with the following as necessary: μ0.)
Homework Equations
Ampere's Law
[itex]\oint B \bullet ds[/itex] = μ0ienc
The Attempt at a Solution
[itex]\oint B \bullet ds[/itex] = μ0ienc
Solving for B:
B[itex]\oint ds[/itex] = μ0ienc
B2∏r = μ0ienc
B = μ0ienc/2∏r
At r < a:
B = 0 because ienc at this point = 0
At a < r < b:
B = μ0ienc/2∏r
I don't know how to get ienc. I know it has something to do with the current density.
At r > b:
ienc = itotal, but I would need an expression for the volume of the cylinder.
V = ∏b2h - ∏a2h
V = ∏h(b2-a2)
Ienc = J0V [itex]\Rightarrow[/itex] Ienc = J0∏h(b2-a2)
B = μ0ienc/2∏r
B = μ0J0h(b2-a2)/2r
However, by including h, I am introducing variables that the problem hasn't allowed me to use.
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