# Math Help - Integration/Electric Flux

1. ## Integration/Electric Flux

I've got a quiz tomorrow on Electric Flux and I'm having a really hard time understanding it. My Prof gave us 4 sample questions to study in preparation for the quiz. If someone could walk me through this first one I'd be extremely grateful.

An uncharged, non-conducting sphere of radius 10cm is placed at the origin. A charge of 2nC is placed at the point $r_{1} = \hat{i} + 2\hat{j} + \hat{k}$ cm. What is the electric flux through the sphere's surface, assuming this is the only charge in the universe?

The answer is $\frac{2 * 10^{-9}}{\epsilon_0}$ .

2. Originally Posted by topher0805
I've got a quiz tomorrow on Electric Flux and I'm having a really hard time understanding it. My Prof gave us 4 sample questions to study in preparation for the quiz. If someone could walk me through this first one I'd be extremely grateful.

An uncharged, non-conducting sphere of radius 10cm is placed at the origin. A charge of 2nC is placed at the point $r_{1} = \hat{i} + 2\hat{j} + \hat{k}$ cm. What is the electric flux through the sphere's surface, assuming this is the only charge in the universe?

The answer is $\frac{2 * 10^{-9}}{\epsilon_0}$ .
1. The charge lies inside the sphere (how do you know that ....?)

2. So Gauss's Law tells you that the electric flux through the closed surface is $\bigcirc \hspace{-1.4em} \int \hspace{-.8em} \int_S E \cdot dS = \frac{q}{\epsilon_0}$.

3. Note that $2 nC = 2 \times 10^{-9} C$.