781_Physics ProblemsTechnical Physics

781_Physics ProblemsTechnical Physics - Chapter 27 P27.56 I...

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Chapter 27 121 P27.56 We find the drift velocity from I nqv A nqv r dd == π 2 v I nq r v x t t x v d ×× = × × = −− 2 28 3 19 2 2 4 3 4 8 1000 8 49 10 1 60 10 10 234 10 200 10 10 8 54 10 27.0 yr A m C m ms m 2.34 m s s .. . . ej e j P27.57 We begin with the differential equation α ρ = 1 d dT . (a) Separating variables, d dT T T 00 zz = ln 0 0 F H G I K J =− TT bg and ρρ = 0 0 e . (b) From the series expansion ex x ≅+ 1 , x << 1 af , 1 . P27.58 The resistance of one wire is 0500 100 50 0 . . mi mi F H G I K J = a f . The whole wire is at nominal 700 kV away from ground potential, but the potential difference between its two ends is IR 500 A k V a f . Then it radiates as heat power P × = VI 50 0 10 1 000 50 0 3 V A M W . P27.59 RA V I A AA A (m) ( ) ( m) 0.540 1.028 1.543 10.4 21.1 31.8 R ΩΩ × × × 141 10
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