What is the purpose of a porous cup in a cell?

Answer 1

You want the eledctrons to move through the electrolyte in the cell but not the bulk chemicals. Full contact between the chemicals will produce a reaction which will destroy the cell quickly.

Answer 2

Hi. I think it's the same principle as described here: http://genchem.chem.wisc.edu/demonstrations/Gen_Chem_Pages/05gasespage/flow_of_gases_through_cup.htm