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Fusilli_Jerry89
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Homework Statement
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)
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________________________________ (z is vertical axis)
Homework Equations
E = q/4(pi)(epsilon)(r^2)
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