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Charge and excess electrons 
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#1
Jan1710, 05:05 PM

P: 19

1. The problem statement, all variables and given/known data
A charged nonconducting rod, with a length of 3.00 m and a crosssectional area of 5.37 cm2, lies along the positive side of an x axis with one end at the origin. The volume charge density ρ is charge per unit volume in coulombs per cubic meter. How many excess electrons are on the rod if ρ is (a) uniform, with a value of 2.54 µC/m3, and (b) nonuniform, with a value given by ρ = bx2, where b = 1.36 µC/m5? 2. Relevant equations F=kQq/r^2 q=volume charge density*area of circle*length 3. The attempt at a solution q=p*(pi)r^2*L=2.54e6C/m^3*5.37cm^2*3.00m=4.09e9 q/e=4.09e9/1.6e19=2.6e10e<this was correct part b: p=bx^2=1.36e6x^2 dq=Apdx dq=5.37e4*1.36e6x^2 dx did the integral procedure and it may be wrong: integral(dq)=7.3032e10 *integral (x^2) from 0 to 2 =1.94e9 q/e=1.94e9/1.6e19 = 1.22e10< marked incorrect I dont know how to fix this. 


#2
Jan1710, 08:04 PM

HW Helper
P: 2,323

Why did to integrate from 0 to 2 if the length of the rod is 3 m?



#3
Jan1710, 08:28 PM

P: 19

I was practicing the example from the book and mistakenly used that value haha... Thanks!



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