posted by physics help .
You want to get an idea of the magnitude of magnetic fields produced by overhead power lines. You estimate that a transmission wire is about 11m above the ground. The local power company tells you that the line operates at 13kV and provide a maximum of 86MW to the local area.
Estimate the maximum magnetic field you might experience walking under such a power line, and compare to the Earth's field. [For an ac current, values are rms, and the magnetic field will be changing.]