# Electric fields of particles

1. Feb 3, 2012

### RET80

1. The problem statement, all variables and given/known data
You want to create an electric field = < 0, 3x10^4,0 > N/C at location < 0, 0, 0>.
Where would you place a proton to produce this field at the origin?

2. Relevant equations
1/4?? * q/r^2 = 3x10^4 N/C

(if you can't see the 1/4th part of the equation it's 1/(4(pi)(epsilon-not)) == 9.0x10^9 or just k)
3. The attempt at a solution
I moved everything over so that I can solve for r^2 and got this as my equation:
r = sqrt((9.0x10^9)(1.6x10^-19)/(3x10^4))

I ended up getting 2.19x10^-7 however its' saying it's not correct. I have it set up as a vector:
<0, 2.19x10^-7, 0>

Does it need to be negative for a proton in relation to the electric field?

Last edited: Feb 3, 2012
2. Feb 3, 2012

### jehan60188

if you place a proton at 2.19E-7 above the x-axis, which way will a +1C charge accelerate when it is placed at the origin?

3. Feb 3, 2012

### RET80

I have nooo idea. I'm kind of hazy as to the magnitude and direction of charged particles, so I'm not sure if its pointing up or down

4. Feb 3, 2012

### jehan60188

like charges (attract or repel) each other

5. Feb 3, 2012

### RET80

Oh wait, if it's at the origin, a proton would move away, so the sign would be negative, wouldn't it?

6. Feb 3, 2012

right