The problem with the discussion of motional emf usually, and with this example in particular, is the definition of the conventional current in the problem, so the left-hand rule can be used. Most people get confused by the electron flow down the bar, which is clearly a current and caused by a magnetic force, and the current that exists because we are dragging electrons in the bar along at velocity v.

The final window in the model (see above) shows the E field set up, resulting in an electric force balancing the magnetic force on the electrons in the rod.

1. Run the model a couple of times and use the left-hand rule to verify that the electrons move as predicted in this simplified model. (The time until the formation of the final equilibrium state is greatly exaggerated in the model.)
2. Use a basic forces balancing argument to show E = Bv and verify that the model is giving sensible charge distributions for various speeds.
3. One difficulty with such a model as this is it simplifies the overall motion of charge in the rod. Can you give an argument thinking about a "sea" of electrons that might suggest why the picture used here is not as bad as it might seem at first?