Two parallel current carrying wires in the same direction attract each other. Which hand method do we use? Is it the opposite direction of electrons to that of the conventional I direction?
1 Answer
It doesn’t matter in this case. You have two relevant conventions, the handed ness of the cross product and the sign of the electron charge. You can switch either or both of those conventions and you get the same result.
The reason is because there are two cross products involved. The first is for determining the direction of the field, and the second is for determining the direction of the force. If you choose a different convention then you get negative signs on both, and two negatives gives a positive.