---
title: "A flat nonconducting disk of radius \\(R\\) carries a total electric charge \\(Q\\) distributed uniformly over its surface. The disk rotates about its central symmetry axis perpendicular to its plane at a constant angular frequency \\(\\omega\\). Which of the following expressions represents the magnitude of the magnetic field at the center of the disk?"
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url: "https://nerd-notes.com/ubq/118558/"
date_modified: "2026-08-04T08:11:21+00:00"
---

# A flat nonconducting disk of radius \(R\) carries a total electric charge \(Q\) distributed uniformly over its surface. The disk rotates about its central symmetry axis perpendicular to its plane at a constant angular frequency \(\omega\). Which of the following expressions represents the magnitude of the magnetic field at the center of the disk?

A flat nonconducting disk of radius \(R\) carries a total electric charge \(Q\) distributed uniformly over its surface. The disk rotates about its central symmetry axis perpendicular to its plane at a constant angular frequency \(\omega\). Which of the following expressions represents the magnitude of the magnetic field at the center of the disk?

![A flat circular disk of radius R lies in a horizontal plane, viewed at a slight tilt. A curved arrow around the vertical central axis indicates rotation with angular frequency \omega. A thin concentric ring element of radius r and width dr is highlighted on the surface. The total charge on the disk is labeled Q. A point at the central axis on the disk plane is labeled O. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1785831081-xBnv8p.jpg)

- **A.** \(\dfrac{\mu_0 Q \omega}{2\pi R}\)
- **B.** \(\dfrac{\mu_0 Q \omega}{4\pi R}\)
- **C.** \(\dfrac{\mu_0 Q \omega}{\pi R}\)
- **D.** \(\dfrac{\mu_0 Q \omega}{8\pi R}\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/118558/*