# Homework Help: Confused by the fractions in the parenthesis

1. Aug 26, 2010

### patm95

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

Given: see attachment

Five additional electrons are placed at the origin. What is the electric field now.

2. Relevant equations

Electric field equations of E=q/(4pi*Eo*r^2)

3. The attempt at a solution

I am wondering if the electric field would just be 50% higher because of adding five electrons. However I am somewhat confused by the fractions in the parenthesis. I know that the electric field is going to be a summation of the charges relative to the distance from a point. I am just unsure how to apply that thought in this case due to my misunderstanding of those fractions in the parenthesis. Thanks!

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2. Aug 26, 2010

### kuruman

Re: Electrostatics

If all you had is five electrons at the origin, what would be the electric field vector as a function of r? If you know the answer, then add that field to the given one and you're done. That's how superposition works.

3. Aug 26, 2010

### patm95

Re: Electrostatics

I think I see where u are coming from. So I basically take the 5e/(4pi*ep*r^2) and add it to the original vector?

4. Aug 26, 2010

### kuruman

Re: Electrostatics

Yes, add it with unit vector r-hat tacked on it.