# Differential problem in Gausses law

From the Gauss law we know, $\nabla \cdot \vec{E} = \rho / \epsilon_0$.

We have given that, $\vec{E}= kr^3 \hat {r}$

Now I have problem to get the identified part. Can you please elaborate that?

• $E_{r} = kr^{3}$. – Felix Marin Jun 18 '14 at 19:18
• I wanted to understand the the previous step? – Complex Guy Jun 18 '14 at 19:21
• That's the formula for divergence spherical coordinates (when the force is radial). Gauss's Law applies to the usual electromagnetic fields (given by inverse square laws), not to an arbitrary $\vec E$. – Ted Shifrin Jun 18 '14 at 19:26