photo electric effect question When EM radiation with fixed intensity and frequency strikes the metal plate, are the outgoing electrons at higher energy if the plate were charged to some potential than if the plate were simply neutral?
 A: If the plate has negative charge, then yes. Freed electrons will be accelerated away from the plate by the electric field, gaining energy above what they acquired from absorbing a photon. 
If the plate is positively charged, then the opposite occurs- moving against an attractive electric field robs the emitted electrons of energy, and the positive charge will pull them back if their initial kinetic energy isn't high enough. Since emitting electrons reduces the negative charge density in the plate, a metal plate that's insulated from any other ready source of electrons will slowly develop a positive charge until it stops emitting electrons due to the potential barrier becoming too high.
A: No, the electric field applied to the metal plate will only take effect once the electron is ejected from the surface (once it has gotten over the work function of the surface) once it is a free electron and assuming it is in a vacuum only then will the electron be accelerated.  In fact this is the principal by which a PM (Photo Multiplier) tube works.  The initial free electron is accelerated and collided with another metal plate at a different potential, which then emits 2 or more electrons, which in turn cascade to a third electrode which multiplies that pulse of electrodes again. etc. etc.
