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## Homework Statement

Assuming that an infinitely long line charge of 50(pC/m) parallel to the y-axis at x=2(m) and z=1(m), determine the electric intensity at the point (-1, 5, -3).

The answer given : -0.18(a

_{x}0.6 + a

_{z}0.8)(V/m)

## Homework Equations

Electric field intensity due to an infinite straight line charge of uniform density :

**E**= a

_{r}("rho" / (2"pi""epsolon 0"r) ( V/m)

## The Attempt at a Solution

I let point P = -a

_{x}+ a

_{y}5 - a

_{z}3

Point on line perpendicular to point P, Q = a

_{x}2 + a

_{z}

Vector Q to P = -a

_{x}3 + a

_{y}5 - a

_{z}4

I found out that if i ignore or make coefficient of a

_{y}to zero and apply the above formula i'll get the answer..

but i do not understand why..please help

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