917_Physics ProblemsTechnical Physics

917_Physics ProblemsTechnical Physics - Chapter 32 P32.67...

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Chapter 32 257 P32.67 From Ampere’s law, the magnetic field at distance rR is found as: Br J r I R r 2 0 2 0 2 2 πµ π µ bg ej == F H G I K J , or B Ir R = 0 2 2 . The magnetic energy per unit length within the wire is then UB rdr I R rd r I R R I RR A = F H G I K J = zz 2 0 0 0 2 4 3 0 0 2 4 4 0 2 2 2 44 41 6 . This is independent of the radius of the wire. P32.68 The primary circuit (containing the battery and solenoid) is an RL circuit with R = 14 0 . , and L NA ×× = −− 0 2 7 2 4 4 10 12500 100 10 00700 0280 A . . H . (a) The time for the current to reach 63.2% of the maximum value is the time constant of the circuit: τ = = L R 00200 200 . .. H 14.0 s m s . (b) The solenoid’s average back emf is ε L f L I t L I t = F H G I K J = F H G I K J ∆∆ 0 FIG. P32.68 where II V R f F H G I K J = F H G I K J = 0632 60 0 271 . . . max V 14.0 A. Thus, L = F H G I K J = 37 9 . . . H A 0.020 0 s V af . (c) The average rate of change of flux through each turn of the overwrapped concentric coil is
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This note was uploaded on 12/14/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .

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