# HW09Sol - Jim Guinns PHYS2212 Assignment#9 Solutions 1 In...

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Jim Guinn’s PHYS2212 Assignment #9 Solutions 1. In an electrical circuit, a current of 3.50A passes through a circuit element for 45.0 seconds. a) How many coulombs is this? b) How many electrons is this? Since I = Q / t , we have Q = I t , so Q = 3.50A 45.0s = Q = 158C , or Q = 158C (1e / 1.602x10 -19 C) = Q = 9.86x10 20 electrons . 2. In a certain particle accelerator, a proton beam with a diameter of 2.00mm constitutes a current of 1.00mA. The kinetic energy of each proton is 20.0MeV. The beam strikes a metal target and is absorbed by it. a) What is the number “n” of protons per unit volume in the beam? Since I = nAev d it follows that n = I / [( π r 2 ) e v d ] . With KE = mv d 2 /2 or v d = (2KE / m) 1/2 = [2 (20x10 6 eV) (1.60x10 -19 J/eV) / (1.67x10 -27 kg)] 1/2 = 6.19x10 7 m/s , so n = (1.0x10 -3 A) / [ π (1.0x10 -3 m) 2 (1.60x10 -19 C) (6.19x10 7 m/s)] = 3.21x10 13 protons/m 3 . b)

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HW09Sol - Jim Guinns PHYS2212 Assignment#9 Solutions 1 In...

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