Potential due to a continuous charge distribution.

Ajwrighter
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1. A nonconducting rod of length L = 6cm and uniform linear charge density A = +3.68pC/M . Take V = 0 at infinity. What is V at point P at distance d = 8.0cm along the rod's perpendicular bisector?



2. V = S E * ds One half of the rod = L/2 1/4piEo = 9x10^9
R = sqrt((L/2)^2 + (D^2)) = 0.08544m




3. I've attempted this solution many times but here is the more recent.
(9x10^9) [(((3.68 x 10^-12)/0.08544 ) * (.03)*(2) ] = .0232584V



My reasoning for this method. Take the Charge density A and divide it by the Range of both sides, then multiply by the length of each side which equals .03 and then multiply it by twice to obtain V from both sides (since both sides are identical.) The problem is the answer in the back gives 24.3mV = .0243V. The method I am using, is it just a close proximity, a lucky guess? Or can my method be reproduced on similar problems to obtain a close proximity? In either case, if my method is wrong what do I need to change?
 
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You have to integrate over the length of the rod.
The calculation is the same as that in many elementary texts for an infinite rod,
but with finite limits on the integral.
 
on one of my previous methods when I integrated I get 0.02484
 
I just tried integrating another way and got 0.02358.
 
To solve this, I first used the units to work out that a= m* a/m, i.e. t=z/λ. This would allow you to determine the time duration within an interval section by section and then add this to the previous ones to obtain the age of the respective layer. However, this would require a constant thickness per year for each interval. However, since this is most likely not the case, my next consideration was that the age must be the integral of a 1/λ(z) function, which I cannot model.
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