Physhw 6-solutions

Physhw 6-solutions - billing (cab4763) hw 6 opyrchal...

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Unformatted text preview: billing (cab4763) hw 6 opyrchal (121104) 1 This print-out should have 13 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points The current in a wire decreases with time according to the relationship I = (1 . 86 mA) e a t where a = 0 . 13328 s 1 . Determine the total charge that passes through the wire from t = 0 to the time the current has diminished to zero. Correct answer: 0 . 0139556 C. Explanation: I = dq dt q = integraldisplay t t =0 I dt = integraldisplay t =0 (0 . 00186 A) e . 13328 s- 1 t dt = (0 . 00186 A ) e . 13328 s- 1 t- . 13328 s 1 vextendsingle vextendsingle vextendsingle vextendsingle vextendsingle = . 0139556 C . 002 10.0 points The drift velocity of free electrons in a cop- per wire is 7 mm / s, resistivity is 1 . 8 10 8 m, and the free electron density is 8 . 43 10 28 electrons / m 3 . Calculate the electric field in the conductor. Correct answer: 1 . 70161 N / C. Explanation: Let : v d = 7 mm / s = 0 . 007 m / s , n = 8 . 43 10 28 electrons / m 3 , = 1 . 8 10 8 m , and q e = 1 . 602 10 19 C / electron . From Ohms law, J = E = E = n q V d E = n q v d = (8 . 43 10 28 electrons / m 3 ) (1 . 602 10 19 C / electron) (0 . 007 m / s) (1 . 8 10 8 m) = 1 . 70161 N / C . 003 10.0 points A conductor with cross-sectional area 6 cm 2 carries a current of 12 A. If the concentration of free electrons in the conductor is 5 10 28 electrons / m 3 , what is the drift velocity of the electrons?...
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This note was uploaded on 03/25/2011 for the course PHYSICS 121 taught by Professor Fayngold during the Spring '10 term at NJIT.

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Physhw 6-solutions - billing (cab4763) hw 6 opyrchal...

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