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title: "A stationary circular conducting loop of radius \\(R\\) lies in a region containing a spatially uniform magnetic field \\(\\vec{B}(t)\\) directed perpendicular to the plane of the loop. The magnitude of the magnetic field varies with time according to \\(B(t) = B_0 e^{-bt}\\), where \\(B_0\\) and \\(b\\) are positive constants. Which of the following best explains the physical mechanism that produces the induced electromotive force (EMF) in the loop?"
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url: "https://nerd-notes.com/ubq/118678/"
date_modified: "2026-08-04T08:13:41+00:00"
---

# A stationary circular conducting loop of radius \(R\) lies in a region containing a spatially uniform magnetic field \(\vec{B}(t)\) directed perpendicular to the plane of the loop. The magnitude of the magnetic field varies with time according to \(B(t) = B_0 e^{-bt}\), where \(B_0\) and \(b\) are positive constants. Which of the following best explains the physical mechanism that produces the induced electromotive force (EMF) in the loop?

A stationary circular conducting loop of radius \(R\) lies in a region containing a spatially uniform magnetic field \(\vec{B}(t)\) directed perpendicular to the plane of the loop. The magnitude of the magnetic field varies with time according to \(B(t) = B_0 e^{-bt}\), where \(B_0\) and \(b\) are positive constants. Which of the following best explains the physical mechanism that produces the induced electromotive force (EMF) in the loop?

![A circular conducting loop of radius R is drawn in the xy-plane. A spatially uniform magnetic field B(t) points out of the page in the +z-direction, represented by five dots with small circles around them evenly distributed inside and around the loop. A text label B(t) sits next to one of the dots. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1785831220-LRAnFT.jpg)

- **A.** The time-varying magnetic flux induces a non-conservative electric field along the loop, which exerts electric forces on charge carriers in the conductor.
- **B.** The time-varying magnetic field exerts a direct magnetic force \(\vec{F}_B = q(\vec{v} \times \vec{B})\) on the stationary charge carriers in the conductor.
- **C.** The uniform magnetic field causes static charge accumulation on opposite sides of the loop, creating a conservative electrostatic field.
- **D.** The spatial gradient of the magnetic field exerts a net magnetic force that propels charge carriers around the loop.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/118678/*