Electric field of moving point charge.

At a particular instant a proton is at the origin, moving with velocity < 5 x 10^4, -2 x 10^4, -7 x 10^4 > m/s. At this instant:

(a) What is the electric field at location < 4 x 10^-3, 2 x 10^-3, 3 x 10^-3 > m, due to the proton?
= <

E = < ___ ,___ ,____ > N/C

-- These are the knowns I have picked up..
-- E = KQ/r^2
-- So if Q is 1.6 x 10^-19, K = 8.99 x 10^9, and r should be the individual (x, y, z distance away)
So when finding E = , shouldn't Ex = KQ / ((4e-3)^2), and Ey = KQ / ((2e-3)^2), and Ez = KQ / ((3e-3)^2) ???
This didn't give me the right answer. I have also tried F = MA = QE, therefore E = MA/Q, still didn't work. Can anyone help me here? I don't need the magnitude of E, I need each individual component of E(Ex, Ey, Ez)..


(b) What is the magnetic field at the same location due to the proton?

B = < ____ , _____ , _____ > T

Your formula for E is the magnitude of the vector;
kQ/r^2 = Sqrt[Ex^2+Ey^2+Ez^2]

try using the component eqs;
Ex = kQx/r^3 , Ey =kQy/r^3 , Ez = kQz/r^3


The Magnetic field is more complicated, requiring the cross product;
B = (uo/4pi)(Q/r^3)(v X r)

you'll have to find the cross product (v X r) in component form and then you can find the various components of "B".
For example;
Bx = (uo/4pi)(Q/r^3)(zvy - yvz)
etc

I believe you can also find the B components by crossing "v" into "E"
B = (1/c^2)(v X E)