Chapter 26, Problem 79P

You’re developing a system to orient an orbiting telescope. The system uses three perpendicular coils, with torques developed in Earth’s magnetic field when current passes through them. Weight limitations restrict you to a length l of wire for each coil. A colleague argues you’ll get the greatest dipole moment and therefore the most torque with a multi-turn coil. You say a 1-turn coil is best. Who’s right?