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roam
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Homework Statement
http://img209.imageshack.us/img209/1508/problemhd.jpg
Homework Equations
The Ampere law: [itex]\oint_C \vec{B} \cdot d\vec{l} = \mu_0 I_{enc}[/itex]
The field and flux is proportional to the current: [itex]\Phi = LI[/itex]
The Attempt at a Solution
(a)
[itex]\oint_C \vec{B} \cdot d\vec{l} = \vec{B} \oint_C d\hat{l}[/itex]
[itex]= \vec{B} (2 \pi s)= \mu_0 I_{enc}[/itex]
[itex]\therefore \ \vec{B}= \frac{\mu_0 I_{enc}}{2 \pi s}[/itex]
The magnetic field is 0 for s<a. So for the space between the conductors do I have to evaluate this between a<s<b?
[itex]\therefore \ \vec{B}= \frac{\mu_0 I_{enc}}{2 \pi b-2 \pi a}[/itex]
Is this correct?
(b) The magnetic flux produced by the current in the conductor in the middle is
[itex]\Phi = \int B.dA = B(2 \pi a h)[/itex]
Here 2πah is the surface area. So how can we evaluate this if we do not know h (height)?
(c) [itex]\Phi = LI \implies L = \frac{\Phi}{I} = \frac{B(2 \pi r h)}{I}[/itex]
Is this the correct approach?
Any help is greatly appreciated.
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