# Conducting rod moving through magnetic field

If a conducting rod moves through a magnetic field which way do its electrons move?

In my revision guide it shows the following picture (more or less, but the following is my drawing of it -- I didn't change anything):

I'm having trouble understanding why the electrons accumulate on the end of the rod shown in the picture. Surely by Fleming's left hand rule the flow of positive charge will be in the direction of the green arrow here:

Which means that the electrons flow in the opposite direction to the green arrow, so the "plus" and "minus" signs in the rod are the wrong way round in this diagram. It should be like:

Or am I doing something wrong?

Thanks!

• Fleming's left hand rule: index finger - field, middle finger - current. – AV23 May 5 '15 at 17:05
• @AV23: Thumb -- thrust (force) – user45220 May 5 '15 at 17:06
• Yes, that too. But I suspect the mistake is in associating quantities to these fingers. – AV23 May 5 '15 at 17:07
• @AV23: No I did it like you said: field -- index finger, current -- middle finger, force -- thumb. But I think I know what I did wrong now, apparently I was meant to use my right hand instead because the current is being generated by motion, not the other way round. physics.stackexchange.com/questions/181260/… – user45220 May 5 '15 at 17:10
• Well, the left hand rule is applicable here too, if you use it the right way - the "current" is due to the "Motion", and the force is where the charges are pushed to on the rod. (All following from $\vec{F} = q\vec{v}\times\vec{B}$) – AV23 May 5 '15 at 17:25

To use rules without knowing what is the reason is boring. See my paper about vector product for Lorentz force, for generators and for electric drives, in a reduced form for perpendicular vectors only. If one isn't sure that this equations could be derived see this answer from mathematicans. See my answer Why does one call $B$ the magnetic induction? too.