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Moving Charges And Magnetism

Question
CBSEENPH12037573

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?

Solution

Given, current, I= 90 A
distance ,r = 1.5 m
Thus,
the magnitude of magnetic field is given by Ampere's circuital law 

               B = μ0I2πr    = 4π×10-7×902π×1.5   = 1.2 × 10-5 T  

Applying the right-hand thumb rule, we find that the magnetic field at the observation point is directed towards south.