# Electric force

1. Mar 1, 2006

### atomant

Some help with this question would be much appreciated. A helium atom has a positively charged nucleus (qnucleus = +2e) with two negatively charged electrons (q = -e) orbiting it. What is the ratio of the electric force acting on one of the electrons due to the nucleus to the force acting on the nucleus due to one of the electrons?

How do I go about finding the ratio of the electric force?.

2. Mar 1, 2006

### Staff: Mentor

What is the formula for electric force.

Then try F(n -> e) / F(e -> n).

It's a bit like asking what is the force with which the earth acts on the moon (or satellite) compared to the moon (or satellite) acting on the earth.

3. Mar 1, 2006

### BerryBoy

Coulombs law.

Use coulombs law to calculate the forces, then divide the force on the electron by the force on the nucleus.

Regards,
Sam

4. Mar 1, 2006

### atomant

So I use F=Kq1q2/r^2. O.k, but hiw do I solve the equations when the values for q or r is not given?. I there something we have to assume in terms of calculation in order to solve this?