P27_046 - 46. (a) Using Eq. 27-11 and Eq. 25-42, we obtain...

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46. (a) Using Eq. 27-11 and Eq. 25-42, we obtain ¯ ¯ ¯ ~ J A ¯ ¯ ¯ = ¯ ¯ ¯ ~ E A ¯ ¯ ¯ ρ = | V A | ρL = 40 × 10 6 V (100 Ω · m)(20 m) =2 . 0 × 10 8 A / m 2 . (b) Similarly, in region B we fnd ¯ ¯ ¯ ~ J B ¯ ¯ ¯ = | V B | ρL = 60 × 10 6 V (100 Ω · m)(20 m) =3 . 0 × 10 8 A / m 2 . (c) With w =1 . 0mand d A =3 . 8 m (so that the cross-section area is d A w ) we have (using Eq. 27-5) i A = ¯ ¯ ¯ ~ J A ¯ ¯ ¯ d A w = ( 2 . 0 × 10 8 A / m 2 ) (1 . 0 m)(3 . 8m)=7 . 6 × 10 8 A . (d) Assuming i A = i B we obtain d B = i B ¯ ¯ ¯ ~ J B ¯ ¯ ¯ w = 7 . 6 × 10 8 A (3 . 0 × 10 8 A / m 2 )(1 . 0m) =2 . 5m . (e) We do not show the graph-and-fgure here, but describe it briefly. To be meaningFul (as a Function oF x ) we would plot V ( x ) measured relative to V (0) (the voltage at, say, the leFt edge oF the fgure, which we are e±ectively setting equal to 0). ²rom the problem statement, we note that
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This note was uploaded on 11/12/2011 for the course PHYS 2001 taught by Professor Sprunger during the Fall '08 term at LSU.

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