# Homework Help: Surface Charge/Electric Field

1. Jul 9, 2008

### Laxman2974

Space vehicles traveling through Earth's radiation belts can intercept a significant number of electrons. The resulting charge buildup can damage electronic components and disrupt operations. Suppose a spherical metallic satellite 0.9 m in diameter accumulates 2.2 µC of charge in one orbital revolution.
(a) Find the resulting surface charge density.
C/m2
(b) Calculate the magnitude of the electric field just outside the surface of the satellite, due to the surface charge.
N/C

2. Relevant equations
a. Looking at the units I need the answer in, I assumed that the surface charge density is charge/area or C/m^2.
for this problem that would be Q /(pie x r^2) or 2.2e^-6C / (pie x .45^2)

So I solved and got 2.2e-6/.6361725124 = 3.458e-6

This is not the right answer - I can't find part a which should be easy - a little help please.

2. Jul 9, 2008

### G01

The satellite is spherical in shape.

The area you have is the area of a circle, not the surface area of a sphere...

3. Jul 9, 2008

### Laxman2974

wow - thanks - I knew there was something obvious I was over looking

4. Jul 9, 2008

### G01

No problem. Glad I could help.