Although the evidence is weak, there has been concern in recent years over possi

Question

Although the evidence is weak, there has been concern in recent years over possible health effects from the magnetic fields generated by electric transmission lines. A typical high-voltage transmission line is 24 m above the ground and carries a 200 A current at a potential of 110 kV. What is the magnetic field strength on the ground directly under such a transmission line? Express your answer to two significant figures and include the appropriate units. What percentage is this of the earth's magnetic field of 50 mu T? Express your answer using two significant figures.

Explanation / Answer

The line can be modelled as a current carring wire. So the magnetic field at strength on the ground will be given by

B = u0 I/2 pi R

B = 4 pi x 10^-7 x 200 / (2 pi x 24) = 16.67 T

Hence, Bwire = 16.67 T

b)Bearth = 50 uT = 50 x 10^-6 T

B(wire)/B(earth) = 16.67/50 x 10^-6 = 3.334 x 10^5

Hence, B(wire)/B(earth) = 3.334 x 10^5

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