Flux from a given charge distribution

[ryukyu]

Homework Statement

Three concentric spherical shells ,r=1m ,r=2m and r=3m, respectively, have charge
distributions 2, −4, and 5 μC/m2.

Calculate the flux through r=1.5m and r=2.5m

Homework Equations

Since we are talking about Gaussian surfaces I assume that the flux at 1.5m is just the flux contained in the 1m shell.

I'm particularly having trouble figuring out what to do with the data. Given that the charge distribution is given in uC/m^2, I assume we need to multiply this by the surface area of each sphere to find the total enclosed charge (Qenc).

Then I have that flux = Q_enc/ε₀. But these answers seem way too high.

The Attempt at a Solution

SA₁=4(pi)r²=4(pi)m²
Q_enc1=4(pi)m²*2uC/m²=8(pi)uC
flux=8(pi)uC/ε₀=2.84x10⁶C
where ε₀=(10^-9/(36*pi))

 

[rl.bhat]

Your answer is correct.

 

[ryukyu]

Thanks for the quick response. The whole mega-Coulomb just had me worried.

 

[rl.bhat]

Thanks for the quick response. The whole mega-Coulomb just had me worried.

It is not mega -Coulomb. Flux is not measured in C, but in Weber.

 

[ryukyu]

I've got it straightened out now. I was assuming eps₀ was unitless. But even given that enlightenment, are these really mega-Webers that seems even more out of scale?

 

[rl.bhat]

No. It is not out of scale.

 

[ryukyu]

Thanks again. I have been working on the homework for this class for at least 30 hours on and off and it's only 7 problems. The professor's method of instruction and my method of learning just don't blend well and that's not his fault, I just need to learn a new way to learn.