PHYS 2212 Module 7.4

Magnetic Force on a Current-Carrying Conductor

7.4 Magnetic Force on a Current-Carrying Conductor

Learning Objectives

By the end of this section, you will be able to:

• Determine the direction in which a current-carrying wire experiences a force in an external magnetic field
• Calculate the force on a current-carrying wire in an external magnetic field

Force on a Current-Carrying Wire

In this circuit, a portion of the wire is immersed in a magnetic field. The length of the wire that is in the field is ℓ. The field has a strength B and points out of the page (as seen from the dots, like a bunch of darts coming right at you, yikes!). Every charge in this wire feels a force from the magnetic field.

Practice!

In the following series of questions, there is a current-carrying straight wire segment (with connecting wires up and out of the page that are not shown) in a uniform magnetic field directed out of the page.

Discuss!

The figure shows a top view of two conducting rails on which a conducting bar can slide. A uniform magnetic field is directed perpendicular to the plane of the figure as shown (into the page, X). A battery is to be connected to the two rails so that when it’s connected, current will flow through the bar and cause a magnetic force to push the bar to the right.

In which orientation, A or B, should the battery be placed in the circuit to result in a magnetic force on the bar that pushes it to the right?

Practice!