A wire carrying a current I is bent into the shape of an exponential spiral, r = eθ, from θ = 0 to θ = 2π as suggested in Figure P29.47. To complete a loop, the ends of the spiral are connected by a straight wire along the x axis. (a) The angle β between a radial line and its tangent line at any point on a curve r = f(θ) is related to the function by
Use this fact to show that β = π/4. (b) Find the magnetic field at the origin.
Figure P29.47
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