[da_coolest]

Cant we make a galvanic cell with only one cell like electrolytic cell? if then why it is impossible?

(without using two separate section for anode reaction and cathode reaction)

[ARGOS++]

Dear da_coolest;

Without dividing both solutions in the known way it would give a very bad galvanic cell, because you may measure a very lousy potential if at all, but no current!

Why?:  If the solution of the less reactive metal reaches the metal which is of higher reactivity, then the whole process would go one only at the less reactive metal according to the examples in:
    http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/redox/home.html  

As you may have seen in the link above, that there is no electron flow from one electrode to the other, but the more reactive metal is anyway gone into solution, and the less reactive metal is deposited (the metal-ion is reduced).
And that means no outer electron-flow!!

I hope to have been of help to you.
Good Luck!
                    ARGOS⁺⁺

[Arkcon]

Like ARGOS⁺⁺: said, failing to separate the electrodes and electrolytes makes for a very poor quality cell.  However, back in the old days, there was a somewhat (and I can only guess about that) commercial cell known as a gravity cell. http://en.wikipedia.org/wiki/Gravity_cell#Gravity_cell  We tend to expect more durability and versatility from our batteries these days.  But it did work, adequately enough, for the applications listed.

[da_coolest]

thanks ARGOS++ and Arkcon. my confusion is almost over! thanks again

[ARGOS++]

Dear Arkcon;

Also in the Gravity-Cell both solutions are "separated", in this case "only" by density-difference!
So in this cell the density "plays" the rule of a diaphragm or ion-separating membrane.

But for sure: A very delicate device!
(With some Agar-Agar you could make it more robust! – And you are just back at the known.)

Good Luck!
                    ARGOS⁺⁺