(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

2 uniformly charged very long (L -> infinite) straight, parallel rods d cm apart each carry a linear charge density +lambda and -lambda.

Find the magnitude and direction of the electric field between the 2 rods (x=0, -d/2 < z < d/2) and above the rods (x=0, z > d/2)

________________________________

---------------------------------------------->x

________________________________ (z is vertical axis)

2. Relevant equations

E = q/4(pi)(epsilon)(r^2)

3. The attempt at a solution

First of all, would E be zero above the 2 rods? The question also has a b part to it that asks what the behavior is if z is much greater than d. I guessed that E was not zero above the 2 rods since it seemed like there were so many marks for finding E above the rods, but was I wrong? If not, do you calculate E above the rods the pretty much the same way as below only subtract them instead of add them?

For E between the rods:

dE = q/4(pi)(epsilon)(x^2 + (d^2)/4)

cos(theta) = (d/2)/(x^2 + (d^2)/4)^.5

dEz = qd/8(pi)(epsilon)(x^2 + (d^2)/4)^3/2

Ez = [qd/8(pi)(epsilon)] * integral from -L/2 to L/2 of (x^2 + (d^2)/4)^-3/2 dx

Ez = qL/2(pi)(epsilon)d

since there are two rods, we multiply this by 2:

E = qL/(pi)(epsilon)d

is this method/approach correct? Thx

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# Homework Help: 1D capacitor, please help

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