920_Physics ProblemsTechnical Physics

920_Physics ProblemsTechnical Physics - 260 Inductance 2U...

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260 Inductance P32.75 (a) It has a magnetic field, and it stores energy, so L U I = 2 2 is non-zero. (b) Every field line goes through the rectangle between the conductors. (c) Φ= LI so L II BdA ya wa == = z Φ 1 L I xdy I y I wy I Ix y dy x y a a =+ F H G I K J zz 1 2 2 2 2 2 2 00 0 0 µ π bg ln . Thus L x a = F H G I K J 0 ln . P32.76 For an RL circuit, It I e RLt af = max : I e R L t max =− = ≅− 11 0 1 9 R L t = 10 9 so R max . .. . = × × −− 314 10 10 2 50 3 16 10 397 10 89 7 25 ej e j yr s yr . (If the ring were of purest copper, of diameter 1 cm, and cross-sectional area 1 mm 2 , its resistance would be at least 10 6 ). P32.77 (a) UL I B × 1 2 1 2 50 0 50 0 10 6 25 10 23 2 10 . H A J (b) Two adjacent turns are parallel wires carrying current in the same direction. Since the loops
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