I encountered this problem during my exam. A coil of 50 turns, each with area 0.02m2 is rotated in a uniform magnetic field of magnitude 0.4T. The coil is rotated at a frequency of 60Hz. Given the average power generated is 50W, what is the resistance of the wire?
E = dΦb/dt
P = E2/R
The Attempt at a Solution
E = dNBA/dt = 50*0.4*0.02/(1/60*1/4) = 96V
(1/60 * 1/4 is the time taken when magnetic flux through the coil is max to zero)
R = 962/50 = 184Ω
However, the correct answer is 227Ω. As the prof had another class to teach, i could not ask him about it. My friend who got the answer said to use another formula: E = ωBAsinωt because Vav is different from Vrms.