Although the evidence is weak, there has been concern in recent years over possible health effects from the magnetic fields generated by tra

Question

Although the evidence is weak, there has been concern in recent years over possible health effects from the magnetic fields generated by transmission lines. A typical high-voltage transmission line is 20 m off the ground and carries a current of 200 A.1. Estimate the magnetic field strength on the ground underneath such a line.2. What percentage of the earth’s magnetic field does this represent?

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Vân Khánh 4 years 2021-08-21T05:34:03+00:00 1 Answers 21 views 0

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  1. thucuc
    0
    2021-08-21T05:36:00+00:00
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    Answer:

    A. B = 6.36 * 10^{-10} T

    B. P ≈ 0

    Explanation:

    In order to calculate the magnetic field strength we have to use the magnetic field strength of a straight wire.

    B = \frac{mi* I}{2\pi *d} (eq. I)

    B = magnetic field strength at distance d

    I = current (A)

    mi = represented by the greek letter μ, represents the permeability of the free space, which is: 4 × π 10^(-7) T m/A

    d = distance from the wire

    By replacing the values in eq I, we have the following:

    B = \frac{4\pi 10^{-7} T m A^{-1} 200 A}{2\pi *20 m}\\\\B = 6.36 * 10^{-10} T\\ (eq II)

    The earth magnetic field in the surface variates from 25 to 65 microteslas. Thus:

    P = Percentage from the wires/percentage of the earth

    P = \frac{6.36 * 10^{-10}T}{65* 10^{-3} T}\\ ∵ B << B_{earth} ∴

    P ≈ 0

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