Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

If we have a spherical capacitor with inner radius or r1 and outer radius of r2, with charges (+/-)q on them and there is a dielectric material (with constant e) in between them with.

What kind of a potential would this create outside the entire capacitor? in the region with the dielectric? and inside the entire thing?

share|cite|improve this question

Using the Gauss's law (see this Link), the solution is as follow, $$ \Phi (r) = \left\{ {\begin{array}{*{20}{c}} {\frac{q}{{4\pi \varepsilon {r_1}}}\,\,\,\,for\,\,\,r \le {r_1}}\\ {\frac{q}{{4\pi \varepsilon r}}\,\,\,\,for\,\,\,{r_1} \le r \le {r_2}}\\ {0\,\,\,\,\,\,\,for\,\,\,r \ge {r_2}} \end{array}} \right. $$

share|cite|improve this answer

This is quite simple as this is a standard equation for the capacitance. You will have

$$C=\epsilon C_0$$

being $C_0$ the capacitance in vacuum. For a full set of formulas in different geometrical configurations see here.

share|cite|improve this answer

You can write down these fields directly without calculating anything because the field of a charged sphere is the same as that of a point charge outside the sphere and zero inside the sphere.

share|cite|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.