Revered Members,
In my attachment, while measuring the angle between current element I(QR) and magnetic field B, they are going in clock wise direction that is from R to Q(shown in Red line), so it is (90 - Θ ) and while measuring the angle between current element I(SP) and B, they are going in anti clockwise direction that is from P to S(shown in Red line), so it is (90 + Θ).
May I get clarification from revered members as to why they have gone in different directions to measure the angle, instead of adopting the same direction, either clockwise or anti clockwise, for measuring the angle in the arms QR and SP?

 

Because they measure the angle according to the direction of current.

 

Because they measure the angle according to the direction of current.

Thanks mik3 for your reply. The current starts from the point P and terminates at Q(for the arm PQ) and similarly it starts from point S and terminates at P(for the arm SP), so what harm in measuring the angle from the starting point rather the terminating point of current in both the arms(PQ and SP)?