Recent content by Troels

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    How to find vector magnetic potential given magnetic field?

    It's important to note that integral is not a universial solution to the poisson equation for A. Most importantly, the current distrubiton has to be localized, among a few other restrictions YOu are almost always off to safer grounds by starting directly from the poisson equation and deduce...
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    How to find vector magnetic potential given magnetic field?

    Don't get me wrong. The equation - like amperes law - is always true, but - likewise like amperes law - it is only useful in finding the magnetude of A along the integration curve - you have to dream up the direction from a symmetry argument. To adress your other question, no. In general you...
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    How to find vector magnetic potential given magnetic field?

    The simplest way to do it, for a general B, is via a PDE problem: \nabla^2 \vec A =-\mu_0\vec J whilst remembering that \nabla\times \vec B =\mu_0\vec J This, togther with suitable boundary conditions, (eg. specifing B on the boundary) should give you the result you are looking for. Please...
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    Need material on anisotropic conductivity

    I've stumbled upon a problem whilst doing my master thesis The problem is to construct the anisotropic conductivity tensor for a material that exhibits Anisotropic magnetoresistance. The problem has left me quite baffled, and coming to think of it, I've never seen a proper treatment of...
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    Finding Magnetic Field in Paramagnetic Aluminum Rod of 35 cm, 10A

    It's right - so just plug-in the magnetization you got from \vec M = \chi \vec H
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    Electromagnetism - Quadrupole , Octupole

    There seems to be missing some information here. How exactly are those multi-poles arranged? equal charges? equal distances? Regular polygons? "a quadupole" or "an octopole" are very wide terms indeed
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    Radius of circle, given 3 points

    Meant Harsh of course. Well I'd say id depends very much indeed on how you define "easy" Indeed, you can't solve a system of quadratic equations using a eg. gauss elimination, but for the linear approach, you still need to construct at least 4 additional "point/slope"-equations, so when it...
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    Radius of circle, given 3 points

    Though technically correct, nonlinear is a bit rash :) Quadratric equations are easy to solve.
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    Finding Magnetic Field in Paramagnetic Aluminum Rod of 35 cm, 10A

    As I stated, it is the current density which is the total current divided by the cross-sectional area of the wire. THat is: J_0=\frac{10\,\mathrm{A}}{\pi(0.35 \,\mathrm{m})^2}
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    Finding Magnetic Field in Paramagnetic Aluminum Rod of 35 cm, 10A

    Okay - that eases thing up a bit :) Use Ampéres law for the H-field: \oint_{\partial \mathcal{S}}\vec H \cdot d\vec \ell = \int_{\mathcal{S}}\vec J_\mathrm{free}\cdot d\vec a For points outside the wire, this of course reduces to the familiar form: \oint_{\partial \mathcal{S}}\vec H...
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    Finding Magnetic Field in Paramagnetic Aluminum Rod of 35 cm, 10A

    Yes. You now have a magnetization inside the rod that prohibits use of the biot-savart law there. Also, I'm not sure what you mean by "35 cm" - are you referring to the length? If so, you should be very careful in applying ampéres law as you do not have a perfect cylindrical symmetry...
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    Infinite potential well/eigenfunction problem

    You know the wave function, and thus everything there is to ever know about the system, including the momentum. Look for an operator \hat p that yield the momentum when it operates on the wavefunction. Then use: \langle p\rangle=\int\psi_0^{*}(x)\hat p \psi_0(x)\, dx
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    Conformal Mapping: Exterior Circle to Interior Hexagon

    It sounds okay - though I seem to recall a mapping that takes the exterior of the circle to the upper half plane in one step. Also when using the Schwarz-Christoffel formula, keep in mind that one of the vertices of the polygon has to map to the point infinity (I once paid dearly in loads of...
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    Radius of circle, given 3 points

    Use the equation for the circle: (x-x_0)^2+(y-y_0)^2=r^2 Inserting the three points give you three equations with three unknows: The x and y coordinates of the cetnerpoint and the radius.
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