# HW01Sol - Jim Guinns PHYS2212 Assignment#1 Solutions 1 A...

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Jim Guinn’s PHYS2212 Assignment #1 Solutions 1. A metal sphere has an initial charge of -8.24mC , then 4.67x10 16 electrons are added to it. What is the final charge on the sphere? (Watch your signs!) Remembering that electrons have a negative charge, and that 1e = 1.602x10 -19 C , we have that the final charge is given by Q = -8.24x10 -3 C + (4.67x10 16 )(-1.602x10 -19 ) = -8.24x10 -3 C – 7.48x10 -3 C = -1.572x10 -2 C = -15.72mC . 2. In the nucleus of an atom, two protons are about 4.25x10 -15 m apart. What is the magnitude of the electric force that one proton exerts on the other? The magnitude of the force is given by Coulomb's Law, and remembering that a proton has a charge of +1e = 1.602x10 -19 C, we have F = k Q 1 Q 2 /r 2 = (8.99x10 9 N m 2 /C 2 ) (1.602x10 -19 C) (1.602x10 -19 C)/(4.25x10 -15 m) 2 = 12.8N . This might seem like a relatively small force, but think about what a tiny particle it is acting on. It is actually HUGE

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## This note was uploaded on 01/23/2012 for the course PYSICS 2212 taught by Professor Jimguinn during the Fall '11 term at Georgia Perimeter.

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HW01Sol - Jim Guinns PHYS2212 Assignment#1 Solutions 1 A...

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