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Unformatted text preview: maini (nm7637) hw7 Shneidman (12108) 1 This printout should have 9 questions. Multiplechoice 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 . What current I flows in the circuit? Correct answer: 0 . 733333 A. Explanation: Let : V = 22 V and R = 30 . The current is I = V R = 22 V 30 = . 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 . Find its diameter. (The resistivity is 5 . 6 10 8 m). Correct answer: 0 . 159358 mm. Explanation: Let : L = 2 . 6 cm = 0 . 026 m , R = 0 . 073 , and = 5 . 6 10 8 m . Resistance is R = L A = L parenleftbigg d 2 parenrightbigg 2 = 4 L d 2 , d = radicalbigg 4 L R = radicalBigg 4 (5 . 6 10 8 m) (0 . 026 m) (0 . 073 )...
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This note was uploaded on 01/31/2011 for the course PHYS 111 taught by Professor Moro during the Spring '08 term at NJIT.
 Spring '08
 moro

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