Previous Answers Notes ASK Example 29.3 The Magnetic Dipole Moment of a Coil Problem A rectangular coil of dimensions 5.40 cm x 8.50 cm consists of 25 turns of wire and carries a current of 20.0 mA. A 0.350 T magnetic field is applied parallel to the plane of the loop. A What is the magnitude of its magnetic dipole moment? B What is the magnitude of the torque acting on the loop? Solution A Because the coil has 25 turns, we modify Equation 29.10 to obtain coil =NIA = (25) (20.0 x 10-3 A) (0.0540m) (0.0850m) B .002295 Equation 29.11 states. τ= μ x B A. m² Because B is perpendicular to coil, the above equation simplifies to give T= coil B = coil (0.350 T) 8.0325e-4 N-m Exercise 29.3 Hints: Getting Started | I'm Stuck A wire is bent into a circular coil of radius r = 5.0 cm with 26 turns clockwise, then continues and is bent into a square coil (length 2r) with 40 turns counterclockwise. A current of 20.0 mA is running through the coil, and a 0.350 T magnetic field is applied to the plane of the coil. (a) What is the magnitude of the magnetic dipole moment of the coil? Hcoil 0.07208 XA m2 Follow the example and calculate the magnetic moments of the circular and square parts individually. How do we combine them? (b) What is the magnitude of the torque acting on the coil? T = N⚫ m