---
title: "An air-filled parallel-plate capacitor has a capacitance of \\(4.0 \\text{ }\\mu\\text{F}\\) and is connected to a \\(30\\text{ V}\\) battery until fully charged. The battery is then disconnected, leaving the capacitor isolated with a fixed charge. An external agent pulls the plates apart slowly until the plate separation is three times its original distance. How much work is done by the external agent in separating the plates?"
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url: "https://nerd-notes.com/ubq/121115/"
date_modified: "2026-08-23T04:58:09+00:00"
---

# An air-filled parallel-plate capacitor has a capacitance of \(4.0 \text{ }\mu\text{F}\) and is connected to a \(30\text{ V}\) battery until fully charged. The battery is then disconnected, leaving the capacitor isolated with a fixed charge. An external agent pulls the plates apart slowly until the plate separation is three times its original distance. How much work is done by the external agent in separating the plates?

An air-filled parallel-plate capacitor has a capacitance of \(4.0 \text{ }\mu\text{F}\) and is connected to a \(30\text{ V}\) battery until fully charged. The battery is then disconnected, leaving the capacitor isolated with a fixed charge. An external agent pulls the plates apart slowly until the plate separation is three times its original distance. How much work is done by the external agent in separating the plates?

- **A.** \(6.0 \times 10^{-4} \text{ J}\)
- **B.** \(1.2 \times 10^{-3} \text{ J}\)
- **C.** \(1.8 \times 10^{-3} \text{ J}\)
- **D.** \(3.6 \times 10^{-3} \text{ J}\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/121115/*