EM6 I Experiment No: EM6 Experiment Name: Magnetic moment of a conducting ring in the magnetic field Objective: Experimentally observation that the magnetic field may have a torque and thus a magnetic moment. Keywords: Torque, Magnetic Dipole Moment Theoretical Information: Figure 6.1: Rectangular current loop in a uniform magnetic field. Consider a rectangular loop carrying a current I in the presence of a uniform magnetic field directed parallel to the plane of the loop, as shown in Figure 6.1. No magnetic forces act on sides 1 and 3 because these wires are parallel to the field. However, magnetic forces do act on sides 2 and 4 because these sides are oriented perpendicular to the field. The magnitude of these forces is ? 2 = ? 4 = 𝐼𝑙? . Considering the right-hand rule, direction of ? 2 is out of the page and direction of ? 4 is into the page. If the loop is pivoted so that it can rotate about point O , these two forces produce a torque about O . The magnitude of this torque, τ , 𝜏 = ? 2 ? 2 + ? 4 ? 2 = (𝐼𝑙?) ? 2 + (𝐼𝑙?) ? 2 = 𝐼𝑙?? 6.1 where the moment arm about O is w/2 for each force. Because of the area of the loop is ? = ?𝑙 , we can express the torque as 𝜏 = 𝐼?? 6.2 Remember that this torque result is valid only when the magnetic field is parallel to the plane of the loop.