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Physics
Classical Physics
Electromagnetism
Magnetic Flux in a Coaxial Cable
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[QUOTE="Charles Link, post: 5465543, member: 583509"] Ampere's law in integral form is perhaps the easiest way to show the magnetic field from the outer conductor is zero. A circular cross section works best, so that the radial symmetry can be applied. Ampere's law in integral form says: ## \oint B \cdot dl =\mu_o I ## where ## I ## is the current through the loop and the integral is around the loop. If there is no current passing through the circular loop (from the outer conductor), by symmetry ## B=0 ##. (At least the tangential component.) Meanwhile, ## B_z=0 ## because the motion of the moving electrical charges is in the z-direction. (by Biot-Savart's law, the ## v \times r ## in the numerator of the Biot-Savart equation for ## B ## tells us that any ## B ## will be perpendicular to ## v ##. Finally ## B_r=0 ## can be shown by using ## \nabla \cdot B=0 ## along with Gauss's law. [/QUOTE]
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Physics
Classical Physics
Electromagnetism
Magnetic Flux in a Coaxial Cable
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