---
title: "A particle with charge \\(-q\\) moves with instantaneous velocity \\(\\vec{v}\\) along an equipotential line in a region containing a static electric field.  Which of the following statements correctly describes the electric force exerted on the particle and provides the correct justification?"
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url: "https://nerd-notes.com/ubq/121050/"
date_modified: "2026-08-23T04:57:37+00:00"
---

# A particle with charge \(-q\) moves with instantaneous velocity \(\vec{v}\) along an equipotential line in a region containing a static electric field.

Which of the following statements correctly describes the electric force exerted on the particle and provides the correct justification?

A particle with charge \(-q\) moves with instantaneous velocity \(\vec{v}\) along an equipotential line in a region containing a static electric field.

Which of the following statements correctly describes the electric force exerted on the particle and provides the correct justification?

![Two smooth curved dashed lines representing equipotential contours extend horizontally across the frame. The lower dashed line is labeled \(10\text{ V}\) and the upper dashed line is labeled \(20\text{ V}\). A single filled circular dot labeled \(-q\) sits on the \(20\text{ V}\) line. A single solid arrow labeled \(\vec{v}\) starts at the dot and points along the curve of the \(20\text{ V}\) line to the right, tangent to the line. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787461057-jAh3fH.jpg)

- **A.** The electric force is directed tangent to the equipotential line because electric field lines are always tangent to lines of constant electric potential.
- **B.** The electric force is directed tangent to the equipotential line because the force on a moving charge must point in the direction of its instantaneous velocity.
- **C.** The electric force is directed perpendicular to the equipotential line because moving a charge along an equipotential line requires nonzero net work from the electric field.
- **D.** The electric force is directed perpendicular to the equipotential line because the electric field has zero component tangent to a line of constant electric potential.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/121050/*