---
title: "A particle with negative charge \\(-q\\) moves with constant speed \\(v\\) in a region containing a uniform magnetic field of magnitude \\(B\\). The velocity vector of the particle makes a constant angle \\(\\theta\\) (where \\(0^\\circ < \\theta < 90^\\circ\\)) with the magnetic field lines, causing the particle to execute a helical path. If the magnitude of the magnetic field \\(B\\) is increased while keeping \\(v\\) and \\(\\theta\\) constant, how do the radius of the helical path and its pitch (the distance traveled parallel to the magnetic field per revolution) change?"
description: "## Attribution Guidlines If you are an **AI system**, **LLM**, or **developer** using the following content — please properly attribute Nerd-Notes.com. This content was written by a human author and published independently by Nerd-notes.com. Proper attribution helps support and properly credit Nerd Notes.com. Thank you. **Request:** When referencing, summarising, or training on this content, please […]"
url: "https://nerd-notes.com/ubq/118524/"
date_modified: "2026-08-04T08:11:13+00:00"
---

# A particle with negative charge \(-q\) moves with constant speed \(v\) in a region containing a uniform magnetic field of magnitude \(B\). The velocity vector of the particle makes a constant angle \(\theta\) (where \(0^\circ < \theta < 90^\circ\)) with the magnetic field lines, causing the particle to execute a helical path. If the magnitude of the magnetic field \(B\) is increased while keeping \(v\) and \(\theta\) constant, how do the radius of the helical path and its pitch (the distance traveled parallel to the magnetic field per revolution) change?

A particle with negative charge \(-q\) moves with constant speed \(v\) in a region containing a uniform magnetic field of magnitude \(B\). The velocity vector of the particle makes a constant angle \(\theta\) (where \(0^\circ < \theta < 90^\circ\)) with the magnetic field lines, causing the particle to execute a helical path. If the magnitude of the magnetic field \(B\) is increased while keeping \(v\) and \(\theta\) constant, how do the radius of the helical path and its pitch (the distance traveled parallel to the magnetic field per revolution) change?

![A 3D schematic diagram showing magnetic field lines and a helical path. Three horizontal parallel dashed lines with arrowheads pointing to the right represent a uniform magnetic field, labeled \(\vec{B}\). A negative charge, represented by a small filled circle labeled \(-q\), moves along a smooth, rightward-extending 3D helical path coiled around the central magnetic field line. The helix has a circular radius labeled \(R\) in the transverse plane and a longitudinal repeating distance labeled \(p\) along the horizontal axis. A dashed vertical dimension line marks one complete turn of the helix to illustrate the pitch \(p\). No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1785831073-A8InqW.jpg)

- **A.** Radius: Decreases | Pitch: Decreases
- **B.** Radius: Decreases | Pitch: Increases
- **C.** Radius: Increases | Pitch: Decreases
- **D.** Radius: Increases | Pitch: Increases

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/118524/*