4. A horizontal overhead power line carries a current of 90 A in east to west direction. What is the magnitude and direction of the magnetic field due to the current 1.5 m below the line?

Answers (1)
S Sayak

The magnitude of the magnetic field at a distance r from a long straight wire carrying current I is given by,

|B|=\frac{\mu _{0}I}{2\pi r}

In this case  (current=35A, distance= 0.2m, permeability of free space = 4\pi \times10-7 TmA-1)

|B|=\frac{4\pi \times 10^{-7}\times 90}{2\pi\times 1.5}=1.2\times10^{-5} T       

   The current in the overhead power line is going from the East to West direction and the point lies below the power line. Applying Maxwell's right-hand thumb rule we can see that the direction of the magnetic field will be towards the South.

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