Question

suppose a certain electric cable can carry a maximum current of 125 A. Determine the magnitude of the magnetic field at a point 4.5 m away from the cable.

    a.  4.69 x 10^-4 T
        b.      3.49 x 10^-5 T
        c.      5.56 x 10^-6 T
        d.      7.95 x 10^-3 T
        e.      1.75 x 10^-5 T

Answer 1

The magnetic field produced by a current carrying wire at a distance "a" from it can be found out using Biot Savart's law and the magnetic field at a point "p" which us "a" metre away from the wire is

B = ₀i/2a

here ₀ is the permeability of the free space

₀ = 4*10^-7 H/m

i is the current flowing through the wire

a is the distance of the point from the wire.

Therefore B = 4*10^-7*125/(2*4.5)

B = 5.56*10^-6 T