(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

An outer shell of charge +Q is insulated by a light thread. There is an inner sphere inside which is earthed. The radii of the outer shell and inner sphere are b and a respectively. What is the potential of a point which is at a distance r from the centre of the inner sphere, where

(i) r=b?

(ii) r=a?

2. Relevant equations

V at r = - [tex]\int charge/ (4\pi\epsilon r^{2})[/tex] from infinity to r

3. The attempt at a solution

Before answering the questions above, I find it difficult to calculate the amount of induced charge on the inner sphere... Because the outer shell having a charge of +Qdoesn't meanthat the inner shell must have an induced charge of -Q.

How can I find the amount of induced charge?

My teacher gave us some hints to solve this question:

the inner sphere is anopensystem as it is earthed

the amount of charge of the inner sphere can be calculated

Besides, I initially thought the potential must be 0 without calculation because it is earthed, but when I tried to do the integration (V = dE/ dr), I couldn't get it as 0 (maybe it's due to the problem that I couldn't find the amount of induced charge of the inner sphere)

Can anyone help me?

thanks!

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# Homework Help: Potential of the inner earthed sphere

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