Currents in dc transmission lines can be 100 A or higher. Some people are concerned that the electromagnetic fields from such lines near their homes could pose health dangers. For a line that has current 180 A and a height of 80 m above the ground, what magnetic field does the line produce at ground level?

B = 4.5 x 10⁻⁷ T = 0.45 μT

Explanation:

From Ampere's law the magnetic field at a certain radius from straight current-carrying wire is given by the following formula:

where,

B = magnetic field = ?

= permeability of free space = 4π x 10⁻⁷ H/m

I = current = 180 A

r = radius = 80 m

Therefore,

B = 4.5 x 10⁻⁷ T = 0.45 μT