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Gee Wiz
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Homework Statement
Two very long coaxial cylindrical conductors are shown in cross-section above. The inner cylinder has radius a = 2 cm and caries a total current of I1 = 1.2 A in the positive z-direction (pointing out of the screen). The outer cylinder has an inner radius b = 4 cm, outer radius c = 6 cm and carries a current of I2 = 2.4 A in the negative z-direction (pointing into the screen). You may assume that the current is uniformly distributed over the cross-sectional area of the conductors. What is Bx, the x-component of the magnetic field at point P which is located at a distance r = 5 cm from the origin and makes an angle of 30o with the x-axis? Bx =?
https://www.smartphysics.com/Content/Media/Images/EM/IE/Bcylinders/pic.gif
Homework Equations
B=(Iμ)/(2πr)
The Attempt at a Solution
Okay so I was able to come up with the correct answer, but I am not sure exactly how. While its nice to get the question right with the snazzy green check mark..it doesn't help in the future. So, I'll try to explain the part where its not clicking for me. I first found the total B at point P. So, i figured i could just use trig to get the x component. I used cosine, which did not yield the correct result, but sine did. I do not understand why i would use sine here. If i treat B as the vector going from the origin to P it looks to me that the correct thing to do would be to use cosine..=/ but its not
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