# Electric Charge Question

1. Jan 29, 2009

### fallen186

1. The problem statement, all variables and given/known data
A nonconducting disk of radius a lies in the z = 0 plane with its center at the origin. The disk is uniformly charged and has a total charge Q. Find Ez on the z axis at the following positions. (Assume that these distances are exact.)

Z = a
[__________]Q / (a2εo) - This is the format the answer should be in.

2. Relevant equations

Ez = $$\frac{kQz}{(z^2+a^2)^{3/2}}$$

k = 1/(2pi*εo)

3. The attempt at a solution
1. Ez = $$\frac{kQz}{(z^2+a^2)^{3/2}}$$

I filled in 'z' and 'k'

2. Ez = $$\frac{Qa}{(a^2+a^2)^{3/2}*2\pi*\epsilon}$$

3. Ez = $$\frac{Qa}{(2a^2)^{3/2}*2\pi*\epsilon}$$

4. Ez = $$\frac{Qa}{8a^{3}*2\pi*\epsilon}$$

5. Ez = $$\frac{Q}{(16\pi*a^{2}*\epsilon}$$

6. $$1/16\pi$$

7. [_.1963495408_]Q / (a2εo) * Its wrong and I don't know what I did wrong. Please help
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Oct 19, 2010