At my school, we are taught the left-hand rule for magnetic force as follows:
But this seems to be completely contrary to Fleming´s Left Hand Rule as originally proposed in 1902:
Suppose you have a wire going into the screen, symbolized by an X, where the south end of the magnetic field is left of the X, and the north end of the magnetic field is right of the X.
S X N
According to the left-hand rule I was taught, the magnetic force will pull the wire down, relative to the 2D screen. According to the original left-hand rule, the magnetic force will pull the wire up, relative to the 2D screen.
Which is correct? One theory I had is that my curriculum has the $B$ field pointing south where by convention it is north, but after looking into it I see that this is not the case, and $B$ always points south by convention.
Is there something I am overlooking, or is this an error in my curriculum that I have to reluctantly accept while I complete this course?
Best Answer
Well, both are essentially the same and not contrary to one another.
Your book teaches you through the direction of flow of electrons, whereas Fleming's left-hand rule uses the direction of flow of current.
And conventionally, the direction of current is the direction of flow of positive charge or you can say, the direction opposite to flow of negative charge. Hence both are depicting the same thing.