HW03-solutions

# HW03-solutions - gilbert(amg3448 – HW03 – tsoi...

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Unformatted text preview: gilbert (amg3448) – HW03 – tsoi – (57210) 1 This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 2) 10.0 points The potential difference in a simple circuit is 16 V and the resistance is 41 Ω. What current I flows in the circuit? Correct answer: 0 . 390244 A. Explanation: Let : V = 16 V and R = 41 Ω . The current is I = V R = 16 V 41 Ω = . 390244 A . 002 (part 2 of 2) 10.0 points How many electrons pass a given point in the circuit in 6 min? Correct answer: 8 . 78049 × 10 20 . Explanation: Let : I = 0 . 390244 A , t = 6 min = 360 s , and q e = 1 . 6 × 10- 19 C . I = q t , where q is in coulombs and t in seconds; that is, q = I t, and the total charge for n electrons is q = n q e , so n = q q e = I t q e = (0 . 390244 A) (360 s) 1 . 6 × 10- 19 C = 8 . 78049 × 10 20 . 003 (part 1 of 2) 10.0 points Consider two conductors 1 and 2 made of the same ohmic material; i.e. , ρ 1 = ρ 2 . Denote the length by , the cross sectional area by A . The same voltage V is applied across the ends of both conductors. The field E is inside of the conductor. V 1 E 1 I 1 1 r 1 V 2 E 2 I 2 2 r 2 If A 2 = 2 A 1 , 2 = 2 1 and V 2 = V 1 , find the ratio E 2 E 1 of the electric fields. 1. E 2 E 1 = 1 2 correct 2. E 2 E 1 = 1 3. E 2 E 1 = 4 4. E 2 E 1 = 8 5. E 2 E 1 = 1 12 6. E 2 E 1 = 1 16 7. E 2 E 1 = 1 4 8. E 2 E 1 = 1 8 9. E 2 E 1 = 1 3 10. E 2 E 1 = 2 Explanation: E 2 E 1 = V 2 2 V 1 1 = 1 2 = 1 2 1 = 1 2 . 004 (part 2 of 2) 10.0 points Determine the ratio I 2 I 1 of the currents . gilbert (amg3448) – HW03 – tsoi – (57210) 2 1. I 2 I 1 = 1 3 2. I 2 I 1 = 4 3. I 2 I 1 = 1 4 4. I 2 I 1 = 8 5. I 2 I 1 = 2 6. I 2 I 1 = 1 2 7. I 2 I 1 = 1 12 8. I 2 I 1 = 1 16 9. I 2 I 1 = 1 correct 10. I 2 I 1 = 1 8 Explanation: I 2 I 1 = V 2 R 2 V 1 R 1 = R 1 R 2 = ρ 1 1 A 1 ρ 2 2 A 2 = 1 A 1 2 1 2 A 1 = 1 . 005 10.0 points Which of the following copper conductor con- ditions has the least resistance? 1. thick, long, and hot 2. thin, long, and hot 3. thin, short, and cool 4. thin, long, and cool 5. thick, long, and cool 6. thin, short, and hot 7. thick, short, and cool correct 8. thick, short, and hot Explanation: We know that the resistance R of a conduc- tor is determined by the resistivity ρ , cross- sectional area A and length : R = ρ A ....
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HW03-solutions - gilbert(amg3448 – HW03 – tsoi...

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