1. The problem statement, all variables and given/known data A uniform non-conducting ring of radius 0.816 cm and total charge 6.76 µC rotates with a constant angular speed of 1.73 rad/s around an axis perpendicular to the plane of the ring that passes through its center. What is the magnitude of the magnetic moment of the rotating ring? r = .00816 m q = 6.76E-6 C ω = 1.73 rad/s 2. Relevant equations μ = IA I = dq/dt A = [itex]\pi[/itex]r^2 3. The attempt at a solution I took the current and said it was equal to qω/2∏, since that gives charge/time. Then I multiplied by area. When that didn't work I decided to take the same approach but integrating from 0 to ∏/2 with r replaced with (rcosθ), to be the radius of any point on the loop, making a circle as a function of angle. Then I said charge was equal to λr dθ, since the charge is uniform. I took that function and integrated it: λω(r^2)/2∫(cosθ)^2 dθ, 0,∏/2. Then I multiplied by 4, for each of the quarters of the loop. The idea is that each infinitesimally small point on the loop has a charge and will behave like a charge orbiting and integrating over all of the possible radii gives the combined magnetic moment. However, this didn't work and I lost points. I don't understand why.