quiz_solutions04

# Fundamentals of Physics, (Chapters 21- 44) (Volume 2)

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PY212 Solutions Quiz 4 This problem is very similar to Sample Problem 26-2 on page 687. The total current flowing through the wire is given by Eq. (26-4): = = JdA A d J i v r where we can ignore the dot product because the current moves parallel to the wire; perpendicular to the cross section of the wire. We cannot write i = JA because J ( r ) is not constant; it depends on r . The current density
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Unformatted text preview: J is constant however inside the area of a thin ring: dr r dA 2 π = (For a derivation of this, look in your calculus books for the infinitesimal area d A = (d r )( r d φ ) in the case of polar coordinates.) Putting things together we find, using R = 0.002 m, A 10 5 . 2 2 2 ) 2 ( 3 × = = =       = ∫ ∫ BR dr B dr r r B i R R...
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