You want to get an idea of the magnitude of magnetic fields produced by overhead

Question

You want to get an idea of the magnitude of magnetic fields produced by overhead power lines. You estimate that a transmission wire is about14 m above the ground. The local power company tells you that the lines operate at 240kV and provide a maximum power of 46MW.

Estimate the magnetic field you might experience walking under one such power line.

Express your answer using two significant figures.

Compare this magnetic field to the Earth's field.

Express your answer using two significant figures.

Explanation / Answer

Power = 46 MW
Potential difference = 240 kV
We know that P = VI
I = 46*103 /240 = 191.67 A
Magnetic field due to a long wire
B = uoI/2Pi*r = 4Pi*10-7*191.67 /(2*Pi*14 ) = 27.38*10-7 T

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