# Thermal power in a coil of wire in magnetic field [closed]

If there is a coil of wire with radius r = 15.4 cm with resistance per unit length λ = 0.331 Ω/m in magnetic field with changing induction B = B0 * cos(ωt), where B0 = 0.35T and ω = 4.1 rad/s and coil is rotating around its diameter with speed ω (at t = 0 the coil is perpendicular to the magnetic field) what is the average thermal power emitted by this coil?

I tried to solve this problem by calculating the amplitude of the emf with equations V = ΔΦ/Δt, Φ = Bπ(r^2)sin(ωt), the amplitude would be B0 * π(r^2). Then calculating the rms value, Vrms = V/√2 and squaring it and dividing it by R = 2πrλ (from P = V^2/R). I calculated P = 0.001061 W, but the site I got this problem from is telling me it's the wrong answer. I'm not sure if talking about emf in closed loop of wire is correct, but I don't know how to deal with this problem otherwise. If someone can tell me what did I do wrong, that would be great. (Sorry for potential language mistakes).

• Hello there, and welcome to the Physics Stack Exchange! Homework and "check my work" questions should ask about a specific physics concept and show some effort to work through the problem. We want our questions to be useful to the broader community, and to future users. Please read this post on asking homework questions and this post for "check my work" questions. Oct 16 at 14:50