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bhdmia

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**Field at End of Line of Charge 2**

A charged rod of length L=7.10 m lies centered on the

*x*axis as shown. The rod has a charge density which varies according to

**λ**=ax^2 where a=−20.2

**μ**C/m^3 .

What is the x component of the electric field at a point on the x-axis a distance of D=3.70 m from the end of the rod?

**Relevant equations: Coulomb's Law - E=kQ/r^2**

**The attempt at a solution:**Ok, so part I of this problem was to calculate the total charge of the rod, which I figured out easily enough. Part II, as stated above, is to find the electric field at some point P along the axis of the line of charge. Here's my attempted solution:

E = ∫ (kdQ/r^2)*<i> where dQ=ax^2dx where r=x. The x^2 on top and x^2 on bottom cancel out so you just end up integrating dx with bounds (D+L) and (L) and multiply by k and a. That didn't work, so I tried the equation with <xi> for the r vector and that didn't work either. I can't figure out what I'm doing wrong. Help!

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