---
title: "A solid copper ring is released from rest above a vertical solenoid that carries a constant direct current. As the ring falls toward the top opening of the solenoid, it experiences an upward magnetic force that opposes its motion. Which of the following best explains the origin of this upward magnetic force?"
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url: "https://nerd-notes.com/ubq/118690/"
date_modified: "2026-08-04T08:13:47+00:00"
---

# A solid copper ring is released from rest above a vertical solenoid that carries a constant direct current. As the ring falls toward the top opening of the solenoid, it experiences an upward magnetic force that opposes its motion. Which of the following best explains the origin of this upward magnetic force?

A solid copper ring is released from rest above a vertical solenoid that carries a constant direct current. As the ring falls toward the top opening of the solenoid, it experiences an upward magnetic force that opposes its motion. Which of the following best explains the origin of this upward magnetic force?

![A vertical cylindrical solenoid with evenly spaced wire windings is depicted along a vertical central axis. Positioned directly above the top opening of the solenoid is a flat, horizontal copper ring. A single straight arrow pointing vertically downward from the center of the ring is labeled v. Dotted magnetic field curves emerge from inside the top of the solenoid and diverge outward to the left and right. At the position of the ring's cross-section, two arrow vectors representing the magnetic field point upward and away from the central axis. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1785831226-2kwGfl.jpg)

- **A.** The time-varying magnetic flux induces a non-conservative electric field in the copper ring, which exerts an upward electrostatic force directly on the neutral atomic lattice of the copper.
- **B.** The induced current in the ring interacts with the purely axial component of the magnetic field, producing a net magnetic force directed vertically upward along the axis.
- **C.** The induced current in the ring interacts with the divergent radial component of the solenoid's fringe magnetic field, producing a net upward magnetic force.
- **D.** The falling ring experiences an upward magnetic force because the induced current flows in a direction that reinforces the solenoid's magnetic flux, creating a strong magnetic attraction toward the region above the ring.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/118690/*