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QPage 139: Q5: HC Verma: Concepts of Physics - Volume 2 Gauss's Law Page 139: Q5 Solution: A point charge q is placed in a cavity in a metal block. If a…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often assume a charge outside a hollow conductor creates a field inside the cavity; however, in electrostatic equilibrium the conductor’s free electrons rearrange so that the electric field within the metal and any enclosed cavity is zero, meaning only the charge inside the cavity (and its induced inner‑surface charge) determines the force on it.

A point charge q is placed in a cavity in a metal block. If a charge Q is brought outside the metal, will the charge q feel an electric force?

Step-by-Step Verified Solution

**Answer:** No, the charge q inside the cavity does not feel an electric force due to the external charge Q. **Step-by-Step Explanation:** The metal block shields the cavity from external fields. Charges on the outer surface redistribute to cancel the external field inside the metal. The cavity field is determined only by the charge q and the induced charges on the cavity walls. The external charge Q does not exert a net force on q (electrostatic shielding) .

All Questions in this Chapter

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