---
title: "Three identical rectangular loops of wire, labeled 1, 2, and 3, have total resistances \\(R\\), \\(2R\\), and \\(3R\\), respectively. Each loop is pulled to the right at the same constant speed \\(v\\) through a boundary out of a region of uniform magnetic field \\(\\vec{B}\\) directed into the page. Which of the following correctly ranks the magnitude of the external force \\(F\\) required to maintain this constant speed while each loop is partially exiting the magnetic field?"
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url: "https://nerd-notes.com/ubq/118696/"
date_modified: "2026-08-04T08:13:47+00:00"
---

# Three identical rectangular loops of wire, labeled 1, 2, and 3, have total resistances \(R\), \(2R\), and \(3R\), respectively. Each loop is pulled to the right at the same constant speed \(v\) through a boundary out of a region of uniform magnetic field \(\vec{B}\) directed into the page. Which of the following correctly ranks the magnitude of the external force \(F\) required to maintain this constant speed while each loop is partially exiting the magnetic field?

Three identical rectangular loops of wire, labeled 1, 2, and 3, have total resistances \(R\), \(2R\), and \(3R\), respectively. Each loop is pulled to the right at the same constant speed \(v\) through a boundary out of a region of uniform magnetic field \(\vec{B}\) directed into the page. Which of the following correctly ranks the magnitude of the external force \(F\) required to maintain this constant speed while each loop is partially exiting the magnetic field?

![A rectangular wire loop of vertical height L and horizontal width w is moving to the right at velocity v across a vertical dashed boundary line. To the left of the boundary line is a uniform magnetic field directed into the page, represented by a grid of eight x symbols. To the right of the boundary line is a field-free region. The left vertical side of the loop is inside the magnetic field region, while the right vertical side is outside. An arrow labeled \vec{v} points to the right from the right edge of the loop, and an arrow labeled \vec{F}_{\text{ext}} also points to the right. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1785831227-79bZZa.jpg)

- **A.** \(F_1 = F_2 = F_3\)
- **B.** \(F_3 > F_2 > F_1\)
- **C.** \(F_1 > F_2 > F_3\)
- **D.** \(F_2 > F_1 > F_3\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/118696/*