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QPage 139: Q3: HC Verma: Concepts of Physics - Volume 2 Gauss's Law Page 139: Q3 Solution: A charge Q is uniformly distributed on a spherical shell. What…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often assume electrostatic shielding applies universally, but it only holds for conducting shells where charges redistribute to cancel the external field. For non-conducting shells, charges are fixed, so the external field penetrates the interior and the net field at the center is non-zero.

A charge Q is uniformly distributed on a spherical shell. What is the field at the centre of the shell? If a point charge is brought close to the shell, will the field at the centre change? Does your answer depend on whether the shell is conducting or non-conducting?

Step-by-Step Verified Solution

**Answer:** The field at the centre is zero. If a point charge is brought close to the shell, the field at the centre remains zero if the shell is conducting. If the shell is non-conducting, the field at the centre may change. **Step-by-Step Explanation:** - For a uniformly charged spherical shell, the field at the centre is zero by symmetry. - **Conducting shell:** When an external charge is brought near, charges redistribute on the shell to cancel the external field inside. The field at the centre remains zero (electrostatic shielding). - **Non-conducting shell:** Charges cannot move. The external charge's field penetrates the shell, and the field at the centre is not zero (it is the field due to the external charge plus the fixed shell charges) .

All Questions in this Chapter

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