(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A 2.0 mm diameter iron ball is charged to +48 nC. What fraction of its electrons have been removed? The density of iron is 7,870 kg/m3.

2. Relevant equations

Q = Ne; N = number of atoms in 1 mole, e is atomic charge, Q = point charge

N = Avagadro's Constant = 6.02E23

Proton Charge = 1.6e-19 C

Electron Charge = -1.6e-19 C

K = (9e9 Nm^2)/(C^2)

vector<E> = (K|q|)/(r^2)

A=4(pi)r^2

D=2r

55.845 is the atomic mass of Iron

3. The attempt at a solution

I know that either the surface area of a sphere, or the Area of the spherical metallic ball comes into play but i do not know which one? i know that electrons will go to the surface of the ball or protons will go to the surface of a ball, and that the conductor internally has an electric field of 0 N/C.

I also know that the density of the iron ball comes into play but have failed at connecting density with charge or even if there is a connection.

I know that it will be a fraction of two things over one another since it is asking for a comparison.

I know that 48nC is 3E11 electrons.

i attempted to solve for E as a vector but got an answer that is way off by more than double.

Q = Ne (6.02E23)(55.845)(1.6E-19) = 5.38E6

I then treated the ball and some other point source as a capacitor using the area of the surface of the sphere, plugging and chugging from this point on but got an incorrect number.

i dont know how to start or tackle this problem :(

**Physics Forums - The Fusion of Science and Community**

# Electron Fraction Calculation based on Density, Avagadro's #, Electrostatic Constant

Know someone interested in this topic? Share a link to this question via email,
Google+,
Twitter, or
Facebook

Have something to add?

- Similar discussions for: Electron Fraction Calculation based on Density, Avagadro's #, Electrostatic Constant

Loading...

**Physics Forums - The Fusion of Science and Community**