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solution6 - fullwood (tf5349) Homework 3 DC Circuits Catala...

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Unformatted text preview: fullwood (tf5349) Homework 3 DC Circuits Catala (12054) 1 This print-out should have 24 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points An X-ray tube used for cancer therapy oper- ates at 4.2 MV with a beam current of 85 mA striking a metal target. Calculate the power of this beam. Correct answer: 3 . 57 10 5 W. Explanation: Let : V = 4 . 2 MV and I = 85 mA . P = I V = (0 . 085 A) (4 . 2 10 6 V) = 3 . 57 10 5 W . 002 10.0 points A wire is made of a material with a resistiv- ity of 8 . 05638 10- 8 m. It has length 4 . 39265 m and diameter 0 . 50739 mm. What is the resistance of the wire? Correct answer: 1 . 75022 . Explanation: Let : = 8 . 05638 10- 8 m , = 4 . 39265 m , and r = 0 . 253695 mm = 0 . 000253695 m . By definition, the resistance of the wire is R = A = r 2 = ( 8 . 05638 10- 8 m ) (4 . 39265 m) (0 . 000253695 m) 2 = 1 . 75022 . 003 (part 1 of 3) 10.0 points A total charge of 9.8 mC passes through a cross-sectional area of a nichrome wire in 3 . 3 s. a) What is the current in the wire? Correct answer: 0 . 0029697 A. Explanation: Let : Q 1 = 9 . 8 mC and t 1 = 3 . 3 s . I = Q t = . 0098 C 3 . 3 s = . 0029697 A . 004 (part 2 of 3) 10.0 points b) How many electrons pass through the cross-sectional area in 49.0 s? Correct answer: 9 . 0947 10 17 . Explanation: Let : q e = 1 . 6 10- 19 C and t 2 = 49 . 0 s . Q = N q e N = Q q e = I t 2 q e = (0 . 0029697 A)(49 s) 1 . 6 10- 19 C = 9 . 0947 10 17 . 005 (part 3 of 3) 10.0 points c) If the number of charges that pass through the cross-sectional area during the given time interval doubles, what is the resulting cur- rent? Correct answer: 0 . 00593939 A. Explanation: Let : Q 2 = 2 Q 1 . fullwood (tf5349) Homework 3 DC Circuits Catala (12054) 2 I = 2 Q 1 t 1 = 2 (0 . 0098 C) 3 . 3 s = . 00593939 A ....
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solution6 - fullwood (tf5349) Homework 3 DC Circuits Catala...

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