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Homework Statement
Find the magnetic field due to a curved wire segment.
Homework Equations
Biot-Savart Law (differential form)
dB=[itex]\frac{\mu_{o}i}{4\pi}[/itex] [itex]\frac{d\vec{S}\times \hat{r}}{r^{2}}[/itex]
The Attempt at a Solution
In class we found the magnetic field at a point in space (point P) caused by the current running through a wire. Point P is equidistant from every point on the wire call this distance R. dS is a differential element that points along the wire and r hat points toward point P. The angle between dS and r hat is 90 degrees at all points.
The point P is essentially the center of a circle and the wire outlines the edge of a circle.
B=[itex]\frac{\mu_{o}i}{4\pi}[/itex]∫[itex]\frac{d\vec{S}\times \hat{r}}{r^{2}}[/itex]
B=[itex]\frac{\mu_{o}i}{4\pi}[/itex]∫[itex]\frac{|d\vec{S}||\hat{r}|sinθ}{r^{2}}[/itex]
B=[itex]\frac{\mu_{o}i}{4\pi R^{2}}[/itex]∫[itex]dS(1)sin90^{o}[/itex]
B=[itex]\frac{\mu_{o}i S}{4\pi R^{2}}[/itex] S=R[itex]θ_{1}[/itex]
where [itex]θ_{1}[/itex] is the angle swept out between one end of the wire and point P and the other end the wire and point P.
B=[itex]\frac{\mu_{o}i R θ_{1} }{4\pi R^{2}}[/itex]
B=[itex]\frac{\mu_{o}i θ_{1} }{4\pi R}[/itex]
OK punchline.
I was thinking how could I find the magnetic field at point P due to a piece of wire that outlines a portion of an ellipse. This would mean that the angle between dS and r hat would be a different angle at every point on the wire and the distance between point P and the wire would be different at every point along the wire.
So the integral would be
B=[itex]\frac{\mu_{o}i}{4\pi}[/itex]∫[itex]\frac{dS sinθ}{r^{2}}[/itex] where S,θ, and r are all variables. How would I integrate this?
dS=drdθ where dθ the angle between dS and r hat and dr is the infinitesimal change of the radius as the integral adds from one end of the wire to the other end.
B=[itex]\frac{\mu_{o}i}{4\pi}[/itex]∫[itex]\frac{drdθ sinθ}{r^{2}}[/itex]
This is as far as I can get. Any help would be appreciated. Thanks.
In retrospect maybe I shouldn't say the wire outlines an ellipse. I just want a wire the satisfies the conditions that the angle between dS and r hat changes at every point along the wire and the distance between point P and the wire changes at every point along the wire. Thanks again.
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