---
title: "A long, tightly wound ideal solenoid of length \\(L\\) with a total of \\(N\\) turns carries a constant direct current \\(I\\). Which of the following pairs correctly gives the magnitude of the magnetic field inside the solenoid near its center, \\(B_{\\text{inside}}\\), and outside the solenoid at a point near its midpoint, \\(B_{\\text{outside}}\\)?"
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url: "https://nerd-notes.com/ubq/118528/"
date_modified: "2026-08-04T08:11:14+00:00"
---

# A long, tightly wound ideal solenoid of length \(L\) with a total of \(N\) turns carries a constant direct current \(I\). Which of the following pairs correctly gives the magnitude of the magnetic field inside the solenoid near its center, \(B_{\text{inside}}\), and outside the solenoid at a point near its midpoint, \(B_{\text{outside}}\)?

A long, tightly wound ideal solenoid of length \(L\) with a total of \(N\) turns carries a constant direct current \(I\). Which of the following pairs correctly gives the magnitude of the magnetic field inside the solenoid near its center, \(B_{\text{inside}}\), and outside the solenoid at a point near its midpoint, \(B_{\text{outside}}\)?

![A horizontal cylindrical solenoid of length L and circular cross-section, wrapped with helical wire turns carrying current I. A central longitudinal dashed axis extends through the center of the cylinder. Two labeled points are shown: point P1 located near the center inside the solenoid, and point P2 located outside the solenoid near its midpoint above the top surface. Arrows along the wire loops show the current direction. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1785831074-iagHnK.jpg)

- **A.** \(B_{\text{inside}} = \dfrac{\mu_0 N I}{2\pi L}\) and \(B_{\text{outside}} = 0\)
- **B.** \(B_{\text{inside}} = \dfrac{\mu_0 N I}{L}\) and \(B_{\text{outside}} = 0\)
- **C.** \(B_{\text{inside}} = \dfrac{\mu_0 N I}{L}\) and \(B_{\text{outside}} = \dfrac{\mu_0 N I}{2\pi L}\)
- **D.** \(B_{\text{inside}} = \mu_0 N I L\) and \(B_{\text{outside}} = 0\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/118528/*