---
title: "Two parallel, frictionless conducting rails separated by a distance \\(\\ell\\) are inclined at an angle \\(\\theta\\) above the horizontal and connected at the top by a resistor of resistance \\(R\\). A uniform, vertically upward magnetic field of magnitude \\(B\\) exists throughout the region. A conducting bar of mass \\(m\\) and length \\(\\ell\\) is released from rest on the rails at time \\(t = 0\\). Which of the following graphs best represents the speed \\(v\\) of the bar as a function of time \\(t\\)?"
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url: "https://nerd-notes.com/ubq/125071/"
date_modified: "2026-09-28T14:14:29+00:00"
---

# Two parallel, frictionless conducting rails separated by a distance \(\ell\) are inclined at an angle \(\theta\) above the horizontal and connected at the top by a resistor of resistance \(R\). A uniform, vertically upward magnetic field of magnitude \(B\) exists throughout the region. A conducting bar of mass \(m\) and length \(\ell\) is released from rest on the rails at time \(t = 0\). Which of the following graphs best represents the speed \(v\) of the bar as a function of time \(t\)?

Two parallel, frictionless conducting rails separated by a distance \(\ell\) are inclined at an angle \(\theta\) above the horizontal and connected at the top by a resistor of resistance \(R\). A uniform, vertically upward magnetic field of magnitude \(B\) exists throughout the region. A conducting bar of mass \(m\) and length \(\ell\) is released from rest on the rails at time \(t = 0\). Which of the following graphs best represents the speed \(v\) of the bar as a function of time \(t\)?

![A line drawing in oblique perspective showing two parallel conducting rails inclined at an angle \(\theta\) to the horizontal, separated by a distance \(\ell\). At the elevated upper ends, the rails are connected by a rectangular resistor labeled \(R\). A straight conducting bar of mass \(m\) and length \(\ell\) rests horizontally across the two rails. A dashed horizontal reference line extends from the bottom of the incline, with an arc indicating the incline angle \(\theta\). Five vertical upward-pointing arrows represent the uniform magnetic field, with one arrow labeled \(\vec{B}\). No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1790604867-UBjFcD.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/125071/*