Lesson: The Torque on a Current-Carrying Rectangular Loop of Wire in a Magnetic Field Physics

In this lesson, we will learn how to calculate the torque on a current-carrying rectangular loop of wire in a uniform magnetic field.

Lesson Plan

Students will be able to

calculate the magnetic torque on a current-carrying rectangular loop of wire in a magnetic field at an angle to the area of the loop using the formula ,
define the magnetic dipole moment of a current-carrying rectangular loop of wire in a magnetic field as the ratio of the torque on the loop to the strength of the magnetic field.

Lesson Presentation

Lesson Video

Lesson Explainer

Lesson Worksheet

Q1:

The diagram shows a rectangular loop of current-carrying wire between the poles of a magnet. The longer sides of the loop are initially parallel to the magnetic field, and the shorter sides of the loop are initially perpendicular to the magnetic field. The loop then rotates through so that all its sides are perpendicular to the magnetic field. Which of the lines on the graph correctly represents the change in the torque acting on the loop as the angle its longest sides make with the magnetic field direction varies from to ?

Q2:

The diagram shows a rectangular conducting coil with 5 turns that is in a magnetic field with a strength of 650 mT. The sides of the loop parallel to line are parallel to the magnetic field, and the sides of the loop parallel to line are perpendicular to the magnetic field. The length of and the length of . The torque on the loop is 1.2 mN⋅m. What is the current in the loop? Answer to the nearest milliampere.

Q3:

The diagram represents a rectangular loop of wire at three different rotational positions in a uniform magnetic field. The wire loop carries a constant current supplied from an external circuit that is not shown in the diagram.

Which color arrows correctly represent the variation in the magnetic force on the loop as it rotates?

Which color arrows correctly represent the variation in the magnetic dipole moment of the loop as it rotates?