Magnetic Force on a Wire

🔖 Topics

• Magnetic force on a current-carrying wire
• Torque on a current-carrying loop

🎯 Objectives

• Solve for the magnetic forces acting on a current-carrying wire in a magnetic field
• Solve for the direction of the forces on a current-carrying wire in a magnetic field using the right-hand rules
• Analyze the torque on a square loop of wire in a magnetic field

📋 Sequence

• Example problems for magnetic force on a wire
• Analysis of the magnetic torque on a loop of wire

🖥️ Animations, Simulations, Activities

• Forces between two current-carrying wires simulation: https://www.geogebra.org/material/show/id/JSrCbknr
• Magnetic torque on a wire loop video: https://www.youtube.com/watch?v=E-3yQqgu8OA

📝 Practice Problems

1. A straight, stiff wire of length 1.00 m and mass 25 g is suspended in a magnetic field B = 0.75 T. The wire is connected to an EMF so that current flows horizontally. How much current must flow in the wire and in what direction so that the tension in the supporting wires is zero? (chapter 19, problem 49 in (Giambattista et al.))

1. A 20 cm by 30 cm rectangular loop of wire carries 1.0 A of current clockwise around the loop. Find the magnetic force on each side of the loop if the magnetic field is 2.5 T out of the page. What is the net magnetic force on the loop? (chapter 19, problem 50 in (Giambattista et al.))

✅ Partial Solutions

1. 0.33 A to the left
2. Top and bottom: 0.75 N; Left and right: 0.5 N; There is no net magnetic force.

📘 Connected Resources

• Animations for Physics and Astronomy. Magnetic Torque. February 2008.
• Giambattista, Alan, et al. College Physics With an Integrated Approach to Forces and Kinematics. 5th ed., McGraw-Hill Education, 2020.
• Newitt, Barb. “Forces Between Two Current-Carrying Wires.” GeoGebra, https://www.geogebra.org/m/JSrCbknr, April 2016.