Question

# A horizontal overhead power line carries a current of 90 A in east towest direction. What is the magnitude and direction of the magneticfield due to the current 1.5 m below the line?

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Solution

## Given: The current carried over power line is 90 A, the distance of the point from the line is 1.5 m. Magnetic field at a point due to power line is given as, B= μ 0 2I 4πr where, the permeability of free space is μ 0 , current carried by the power line is I , and the distance of the point is r. By substituting the given values in the above equation, we get, B= 4π× 10 −7 ×2×90 4π×1.5 =1.2× 10 −5  T Therefore, the magnetic field at a point due to power line is 1.2× 10 −5  T. From right hand thumb's rule, the direction of the magnetic field at the observation point is towards the south.

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