Someone who knows what they are talking about: Show what the magnitude of induced emf 1. The problem statement, all variables and given/known data Consider a magnetic field B = K(x3z2,0, -x2z3)sinωt in the region of interest, where K and ω are positive constants and t is variable time. Show that the magnitude of the induced emf around a circle R in the plane z = a with its center at x = 0, y = 0, z = a is: ε = (K/4)∏a3R4ωcosωt 2. Relevant equations Fluxb = ∫B . dA 3. The attempt at a solution Since the normal vector points in the k direction, we only have to worry about Bz. ∫Bzdydx. So -∫∫(sinwt)x2a3dydx. The make the change to polar: -aK3∫∫(sinwt)(rcosθ)2r dr dθ = -(K/4)a3R4∫cosθsin(wt) dθ. This doesn't get me anywhere. I'm not really sure what I'm supposed to be integrating over, which is probably why I'm stuck.