---
title: "An uncharged, hollow spherical conducting shell has inner radius \\(a\\) and outer radius \\(b\\). A small object carrying a positive charge \\(+Q\\) is suspended on an insulating thread and positioned at the center of the cavity. While the charged object remains at the center, the outer surface of the shell is momentarily connected to ground and then disconnected. After the charged object is completely removed from the cavity without touching the shell, what are the final net charges on the inner surface and outer surface of the shell?"
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url: "https://nerd-notes.com/ubq/121133/"
date_modified: "2026-08-23T04:58:14+00:00"
---

# An uncharged, hollow spherical conducting shell has inner radius \(a\) and outer radius \(b\). A small object carrying a positive charge \(+Q\) is suspended on an insulating thread and positioned at the center of the cavity. While the charged object remains at the center, the outer surface of the shell is momentarily connected to ground and then disconnected. After the charged object is completely removed from the cavity without touching the shell, what are the final net charges on the inner surface and outer surface of the shell?

An uncharged, hollow spherical conducting shell has inner radius \(a\) and outer radius \(b\). A small object carrying a positive charge \(+Q\) is suspended on an insulating thread and positioned at the center of the cavity. While the charged object remains at the center, the outer surface of the shell is momentarily connected to ground and then disconnected. After the charged object is completely removed from the cavity without touching the shell, what are the final net charges on the inner surface and outer surface of the shell?

![A cross-sectional view of a thick spherical conducting shell with inner radius \(a\) and outer radius \(b\). The shell wall between radii \(a\) and \(b\) is shaded gray. At the center of the hollow circular cavity, a small solid circle is labeled \(+Q\), suspended from above by a vertical dashed line. An arrow pointing from the center to the inner boundary is labeled \(a\), and an arrow pointing from the center to the outer boundary is labeled \(b\). A small switch connects the outer surface of the shell to a three-line ground symbol. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-diag-1-1787461094-p8mhmA.jpg)

- **A.** Inner surface: \(-Q\) | Outer surface: \(0\)
- **B.** Inner surface: \(-Q\) | Outer surface: \(+Q\)
- **C.** Inner surface: \(0\) | Outer surface: \(-Q\)
- **D.** Inner surface: \(0\) | Outer surface: \(0\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/121133/*