---
title: "Two large, parallel nonconducting sheets carrying uniform surface charge densities \\(+\\sigma\\) and \\(-\\sigma\\) are fixed a distance \\(d\\) apart in a vacuum. A neutral, uncharged conducting slab of thickness \\(t\\) (where \\(t < d\\)) and area \\(A\\) matching the sheets is placed in the space between the sheets, parallel to them.  Which of the following claims correctly describes the change in the total electrostatic potential energy of the system after the conducting slab is inserted, and provides the correct physical justification?"
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url: "https://nerd-notes.com/ubq/118128/"
date_modified: "2026-08-04T08:05:21+00:00"
---

# Two large, parallel nonconducting sheets carrying uniform surface charge densities \(+\sigma\) and \(-\sigma\) are fixed a distance \(d\) apart in a vacuum. A neutral, uncharged conducting slab of thickness \(t\) (where \(t < d\)) and area \(A\) matching the sheets is placed in the space between the sheets, parallel to them.

Which of the following claims correctly describes the change in the total electrostatic potential energy of the system after the conducting slab is inserted, and provides the correct physical justification?

Two large, parallel nonconducting sheets carrying uniform surface charge densities \(+\sigma\) and \(-\sigma\) are fixed a distance \(d\) apart in a vacuum. A neutral, uncharged conducting slab of thickness \(t\) (where \(t < d\)) and area \(A\) matching the sheets is placed in the space between the sheets, parallel to them.

Which of the following claims correctly describes the change in the total electrostatic potential energy of the system after the conducting slab is inserted, and provides the correct physical justification?

![A schematic diagram showing two vertical parallel sheets separated horizontally by distance d. The left sheet is labeled +\sigma and the right sheet is labeled -\sigma. In the space between them, a rectangular conducting slab of thickness t is positioned parallel to the sheets. Dashed vertical dimension lines indicate the distance d between the sheets and the thickness t of the slab. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1785830721-eabQz0.jpg)

- **A.** The total electrostatic potential energy increases because an external agent must do positive work to polarize the neutral conducting slab.
- **B.** The total electrostatic potential energy remains unchanged because the net charge on the conducting slab is zero and the charge on the sheets is fixed.
- **C.** The total electrostatic potential energy decreases because the magnitude of the electric field in the regions outside the slab drops to \(\dfrac{\sigma}{2\varepsilon_0}\).
- **D.** The total electrostatic potential energy decreases because the electric field inside the conducting slab becomes zero while the field outside remains unchanged, reducing the total volume in which energy is stored.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/118128/*