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ohw13-solutions - Reilly(mar3978 ohw13 turner(56725 This...

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Reilly (mar3978) – ohw13 – turner – (56725) 1 This print-out should have 18 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 6) 10.0 points Consider two conductors made out of the same material; i.e. , they have the same re- sistivity. The material is ohmic. V 1 vector E 1 I 1 1 r 1 V 2 vector E 2 I 2 2 r 2 If A = π r 2 , ρ 2 = ρ 1 , r 2 = 2 r 1 , 2 = 2 1 , and V 2 = V 1 , what is the ratio E 2 E 1 , where E 1 and E 2 are the electric fields inside of conductor 1 and of conductor 2, respectively? 1. E 2 E 1 = 1 4 2. E 2 E 1 = 1 8 3. E 2 E 1 = 1 4. E 2 E 1 = 2 5. E 2 E 1 = 1 2 correct 6. E 2 E 1 = 4 7. E 2 E 1 = 8 Explanation: We know that the potential across a dis- tance l with a constant electric field E is V = E l . The ratio is E 2 E 1 = V 2 2 V 1 1 = 1 2 = 1 2 . 002 (part 2 of 6) 10.0 points What is the ratio J 2 J 1 of the current densities? 1. J 2 J 1 = 8 2. J 2 J 1 = 1 4 3. J 2 J 1 = 1 2 correct 4. J 2 J 1 = 1 5. J 2 J 1 = 4 6. J 2 J 1 = 1 8 7. J 2 J 1 = 2 Explanation: vector J = σ vector E The material is ohmic, and σ 1 = σ 2 , so J 2 J 1 = σ 2 E 2 σ 1 E 1 = 1 2 003 (part 3 of 6) 10.0 points What is the ratio v d, 2 v d, 1 of the magnitudes of the drift velocities? 1. v d, 2 v d, 1 = 1 2. v d, 2 v d, 1 = 1 4 3. v d, 2 v d, 1 = 1 2 correct 4. v d, 2 v d, 1 = 1 8 5. v d, 2 v d, 1 = 2 6. v d, 2 v d, 1 = 4 7. v d, 2 v d, 1 = 8 Explanation: vector J = n qvectorv d
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Reilly (mar3978) – ohw13 – turner – (56725) 2 Since the conductors are made out of the same material, the density of charge carriers must be the same ( n 1 = n 2 ), so v d, 2 v d, 1 = J 2 n 2 q J 1 n 1 q = J 2 J 1 = 1 2 . 004 (part 4 of 6) 10.0 points What is the ratio σ 2 σ 1 of the conductivities? 1. σ 2 σ 1 = 8 2. σ 2 σ 1 = 1 correct 3. σ 2 σ 1 = 1 4 4.
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  • Spring '10
  • TURNER,J
  • SEPTA Regional Rail, Jaguar Racing, Series and parallel circuits, Highways in Slovakia, equivalent resistance, Reilly

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