---
title: "Two long, straight, parallel wires separated by a distance \\(d\\) carry currents \\(I_1\\) and \\(I_2\\) in the same direction, resulting in an attractive magnetic force per unit length of magnitude \\(\\dfrac{F_0}{L}\\). The current in the first wire is changed to \\(3I_1\\), the current in the second wire is changed to \\(\\dfrac{1}{2}I_2\\), and the distance between the wires is increased to \\(2d\\). What is the new magnetic force per unit length between the wires?"
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url: "https://nerd-notes.com/ubq/116327/"
date_modified: "2026-08-03T12:23:28+00:00"
---

# Two long, straight, parallel wires separated by a distance \(d\) carry currents \(I_1\) and \(I_2\) in the same direction, resulting in an attractive magnetic force per unit length of magnitude \(\dfrac{F_0}{L}\). The current in the first wire is changed to \(3I_1\), the current in the second wire is changed to \(\dfrac{1}{2}I_2\), and the distance between the wires is increased to \(2d\). What is the new magnetic force per unit length between the wires?

Two long, straight, parallel wires separated by a distance \(d\) carry currents \(I_1\) and \(I_2\) in the same direction, resulting in an attractive magnetic force per unit length of magnitude \(\dfrac{F_0}{L}\). The current in the first wire is changed to \(3I_1\), the current in the second wire is changed to \(\dfrac{1}{2}I_2\), and the distance between the wires is increased to \(2d\). What is the new magnetic force per unit length between the wires?

![Two vertical, long parallel line segments representing thin wires are separated horizontally by a distance labeled d. Arrows along both wires point upward, labeled I_1 for the left wire and I_2 for the right wire. A horizontal dashed line segment with arrowheads at both ends spans between the wires and is labeled d. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1785759807-9TuEvn.jpg)

- **A.** \(\dfrac{3}{4} \dfrac{F_0}{L}\)
- **B.** \(\dfrac{3}{2} \dfrac{F_0}{L}\)
- **C.** \(3 \dfrac{F_0}{L}\)
- **D.** \(6 \dfrac{F_0}{L}\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/116327/*