Two identical circular loops, P and Q, each of radius r and carrying equal currents arekept in the parallel planes having a common axis passing through O. The direction of current in P is clockwise and in Q is anti-clockwise as seen from O which is equidistant from the loops P and Q. Find the magnitude of the net magnetic field at O.

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Answers

2016-02-15T19:09:19+05:30
The standard formula for field at an axial point is given as 
(see attachment)

Now, as the current flowing in loop P is clockwise by using right hand thumb’s rule the direction of the magnetic field will be towards left and as the current in loop Q is clockwise then the direction of magnetic field is towards left. So the net magnetic field at point O will be the sum of the magnetic fields due to loops P and Q.Also, as the fields produced are at an equal distance to O, BP = BQ,So, net field

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