---
title: "A coaxial cable consists of a long, solid cylindrical inner conductor of radius \\(a\\) and a thin cylindrical outer shell of radius \\(b\\). The inner conductor carries a uniformly distributed current \\(I\\) out of the page, and the outer shell carries an equal current \\(I\\) into the page. Which graph best represents the magnitude of the magnetic field \\(B\\) as a function of distance \\(r\\) from the central axis of the cable?"
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/118612/"
date_modified: "2026-08-04T08:11:48+00:00"
---

# A coaxial cable consists of a long, solid cylindrical inner conductor of radius \(a\) and a thin cylindrical outer shell of radius \(b\). The inner conductor carries a uniformly distributed current \(I\) out of the page, and the outer shell carries an equal current \(I\) into the page. Which graph best represents the magnitude of the magnetic field \(B\) as a function of distance \(r\) from the central axis of the cable?

A coaxial cable consists of a long, solid cylindrical inner conductor of radius \(a\) and a thin cylindrical outer shell of radius \(b\). The inner conductor carries a uniformly distributed current \(I\) out of the page, and the outer shell carries an equal current \(I\) into the page. Which graph best represents the magnitude of the magnetic field \(B\) as a function of distance \(r\) from the central axis of the cable?

![Cross-sectional view of a coaxial cable centered at the origin. An inner solid circular conductor of radius a is shaded light gray and labeled with radius a and current I directed out of the page, indicated by dot symbols. Surrounding it is an outer thin cylindrical shell of radius b, labeled with radius b and current I directed into the page, indicated by x symbols. The region between r = a and r = b is unshaded empty space. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1785831107-pMev3R.jpg)

- **A.** Graph A
- **B.** Graph B
- **C.** Graph C
- **D.** Graph D

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/118612/*