- #1
XCBRA
- 18
- 0
Homework Statement
The polarizatiob charge on the surface of a spherical capacitor is [tex] -\sigma_e \cos(\theta), [/tex] at a point whose radius vector from the centre makes an angle [itex] \theta [/itex] witha given axis Oz. Prove that the field strength at the centre is [tex] \frac{\sigma_e}{3 \epsilon_0}, [/tex]
Homework Equations
The Attempt at a Solution
Well I not entirly sure how to approach this problem. I tried exapanding the potentials inside and outside the sphere as:
[tex] V_{in} = A_1 r \cos(\theta) + \frac{A_2}{r^2}\cos(\theta)
V_{out} = B_1 r \cos(\theta) + \frac{B_2}{r^2}\cos(\theta) [/tex]
Then since [itex] V_{in} \neq \infty, [/itex] [itex] A_2 = 0 ,[/itex]
then saying that at r=R: [itex] D^{perpendicular}_{in} - D^{perpendicular}_{out} = \sigma_f [/itex] and assuming that both inside and outside have the same permitivitty then [tex] E^{radial}_{in} - E^{radial}_{out} = \frac{\sigma_f}{\epsilon_0} [/tex].[tex] A_1 + B_1 - \frac{B_1}{R^2} = \frac{\sigma_e}{\epsilon_0} [/tex]
I am not entirely sure if I am aproaching this problem in the right way. Any help or advice on how to g o about solving this problem or problems like this would very much apreciated.
Last edited: