# Homework Help: Flux and nonconducting shells

1. Apr 5, 2010

### seraphimhouse

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

Flux and nonconducting shells. A charged particle is suspended at the center of two concentric spherical shells that are very thin and made of nonconducting material. Figure (a) below shows a cross section. Figure (b) below gives the net flux Φ through a Gaussian sphere centered on the particle, as a function of the radius r of the sphere. The scale of the vertical axis is set by Φs = 17.0 × 10^5 N·m^2/C. (a) What is the charge of the central particle? Give your answers in µC. What are the net charges of (b) shell A and (c) shell B?

http://edugen.wiley.com/edugen/courses/crs1650/art/qb/qu/c23/pict_23_12.gif

2. Relevant equations

EoI = qenc

3. The attempt at a solution

So I got the measurement of each scale on the graph by dividing Φs by 5 which gave me: 3.4x10^5 N m^2/C

For a) I used EoI = qenc and got 6.018 C which was correct.

now for part b) I found the flux to be -13.6x10^5 N m^2/C. Now finding that I was able to find the q for that area. I found the area to be -1.2036x10^5 C. Now in order to find the net charge for shell a, I subtracted the charge of the central particle which was found in part a) to the charge found in part b) which gave me -1.8054x10^-5 C. But that answer was wrong.

I must have the logic wrong for part b). Can anyone help me out :)

2. Apr 5, 2010

### collinsmark

Are you sure that you are entering your data in units of $$\mu C$$?

3. Apr 5, 2010

### seraphimhouse

yes I have converted them to nano C

4. Apr 6, 2010

### collinsmark

Don't you mean micro coulombs? For example, if your calculated answer was -1.8054x10^-5 C, which is -18.054x10-6 C, which is -18.054 µC, meaning you should enter in -18.054.