You want to get an idea of the magnitude of magnetic fields produced by overhead power lines. You estimate that two wires are each about 30m above the ground and are about 3m apart. The local power company tells you that the lines operate at 10kV and provide a maximum of 40MW to the local are. Estimate the maximum magnetic field you might experience walking under these power lines, and compare to the Earth’s field.[from an ac current, values are rms, and the magnetic field will be changing.]