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It is just a convention so all the signs are in the correct direction.
Real current is the flow of negatively charged electrons yet we still stick to the convention that current flows from positive to negative.
Think about X, Y and Z cartesian coordinate system. This also follows the right hand rule for obvious reasons.
Cross products in vectors also come to mind.
In a mirror Universe the left hand system would be just as valid. Consistency is the only consideration.
Clockwise derives its direction from sundials in the northern hemisphere.
In the southern hemisphere sundials run anticlockwise.
Bert
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