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Electric Field at a Point 
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#1
Feb2413, 03:05 PM

P: 9

1. The problem statement, all variables and given/known data
A charged rod of length L = 1.00 m lies centered on the x axis as shown. The rod has a linear charge density which varies according to λ = ax where a = −90.0 μC/m. What is the x component of the electric field at a point on the x axis a distance of D = 2.00 m from the end of the rod? 2. Relevant equations E=kQ/r^2 charge density = Q/A 3. The attempt at a solution I really do not understand...Where do I get the r from? Since its not uniformly distributed how can there be any field outside? Would my r = (D(half of L))? I'm assuming lambda is just regular charge density at a location of x? 


#2
Feb2413, 03:44 PM

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P: 26,160

Hi Broem!
(and of course it's a linear charge density, ie coulombs per metre, not per metre^{3} ) 


#3
Feb2413, 04:11 PM

P: 9

Thanks for the quick response!!
Ok so here's where I am: I now know that lambda = Q/L so Q = L * (lambda) So I'm left with 9e9(9e6)/(2.5)^2 This however is not the correct answer...Where can I go from here? 


#4
Feb2413, 04:18 PM

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Electric Field at a Point
oh, no, you'll have to integrate …
use coulomb's law to find the electric field from a tiny section [x,x+dx] (whose charge will be λdx, and which you can assume is concentrated entirely at x), and integrate from L/2 to L/2 


#5
Feb2513, 09:26 AM

P: 9

I got it!!!
Thank you so much for your help!!! 


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