# Calculating Electric Fields

• Squall

## Homework Statement

A π- ("pi-minus") particle, which has charge -e, is at location ‹ 5.00e-9, -5.00e-9, -6.00e-9 › m. What is the electric field at location < -5.00e-9, 3.00e-9, 5.00e-9 > m, due to the π- particle?
5e-9 is equivalent to 5*10^-9

E=(k*q/r^2)r-hat

## The Attempt at a Solution

So to find the Electric field created at the given position first I subtract the source from the observation, I am assuming the pi- particle is the source. When I do this is what I get
<-10e-9,8e-9,11e-9>

So next I compute the r^2 or the distance from source to observation location. To do this I square each entry in the vector above and add them up to get 8.5e-17

Now I compute the value to the left of the r-hat vector: 9e9*(-1.602e-19/8.5e-17), this gives me -16962352.94 N/C

Next I calculate the r-hat vector by dividing r by its magnitude which is sqrt(8.5e-17).
I get <-1.0846, .8677, 1.1931>

[-16962352.94 N/C *<-1.0846, .8677, 1.1931>]
Finally I multiply the two numbers together and get a vector with huge values, which doesn't seem right, can some one tell me where I am going wrong or maybe tell me the right way to approach this problem, because I seem to be stuck.

Your value for |r|2 looks dubious. Better check it.

Yes the |r|^2 was dubious

After reworking that I got |r|=1.6882e-8

Plugging this back in I get
E=[9e9*(1.602e-19)/(1.6882e-8)^2]*< -0.5923, 0.4739, 0.6516>

=<2996700,-2397300,-3296300>

Is this a more reasonable answer?

The results look good.

You might want to use scientific notation and appropriate significant figures for your final answer.