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# solution7_pdf - maini(nm7637 hw7 Shneidman(12108 This...

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maini (nm7637) – hw7 – Shneidman – (12108) 1 This print-out should have 9 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 22 V and the resistance is 30 Ω. What current I flows in the circuit? Correct answer: 0 . 733333 A. Explanation: Let : V = 22 V and R = 30 Ω . The current is I = V R = 22 V 30 Ω = 0 . 733333 A . 002 (part 2 of 2) 10.0 points How many electrons pass a given point in the circuit in 9 min? Correct answer: 2 . 475 × 10 21 . Explanation: Let : I = 0 . 733333 A , t = 9 min = 540 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 . 733333 A) (540 s) 1 . 6 × 10 19 C = 2 . 475 × 10 21 . 003 10.0 points A 2 . 6 cm length of tungsten filament in a small lightbulb has a resistance of 0 . 073 Ω. Find its diameter. (The resistivity is 5 . 6 × 10 8 Ω · m). Correct answer: 0 . 159358 mm. Explanation: Let : L = 2 . 6 cm = 0 . 026 m , R = 0 . 073 Ω , and ρ = 5 . 6 × 10 8 Ω · m . Resistance is R = ρ L A = ρ L π parenleftbigg d 2 parenrightbigg 2 = 4 ρ L π d 2 , d = radicalbigg 4 ρ L π R = radicalBigg 4 (5 . 6 × 10 8 Ω · m) (0 . 026 m) π (0 . 073 Ω) × parenleftbigg 1000 mm 1 m parenrightbigg = 0 . 159358 mm .

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• Spring '08
• moro
• Resistor, SEPTA Regional Rail, Jaguar Racing, Electrical resistance, Series and parallel circuits, Jenkintown-Wyncote

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