# Homework Help: Which way does the electric field go in this question?

1. Jun 21, 2014

### mistermill

1. The problem statement, all variables and given/known data

Find the electric field midway between a -3.0nC charge and a -5.0 nC charge that are separated by 0.60 m.

2. Relevant equations

ε= kq/r2

3. The attempt at a solution

net ε = ε1 + 2

I drew my -3.0 charge on the left and my -5.0 charge on the right

midway in between is 0.3 m

they are both negative charges, so the fields lines are towards each charge (away from the centre) and the -5.0 charge has more lines, because it has the bigger charge

so I solved for ε 1 and got -300 N/C
I solved for ε 2 and got -500 N/C

I think that ε 1 should be subtracted from ε 2 so the result is

-200 N/C

The field overall, I think should point toward the larger negative charge

it should point toward the -5.0 nC charge, in my drawing, to the RIGHT.

is that correct?

Thanks!

Last edited: Jun 21, 2014
2. Jun 21, 2014

### SammyS

Staff Emeritus
Yes, the field at the midpoint, points toward the -5.0 nC charge.