Capacitance of two unequally charged conductors After reading many books I now understand that the combination of two conductors having equal and opposite charge placed close to each other forms a capacitor and their Capacitance is defined as the ratio of charge on the capacitor(i.e. the charge on the positive plate) to the potential difference between the two conductors constituting the capacitor. 
Now my question is that is there any meaning of capacitance for two conductors having unequal charges(i.e. the sum of charges is not equal to zero). If yes then how is the capacitance defined for such a system and will the system still be called a capacitor ?
NOTE - I'm a high school student  
 A: Wonderful question!
I'll take a special case here for simplicity, but you can generalise it for any case.
I have 2 conducting parallel plates. One has a charge Q, another is neutral. (Note that you can use this method for any charge on any capacitor).
Note that I mentioned "Conducting" plates. How does this help?
This says that any charge distribution happens only on the surfaces, and it happens such that the total electric field in the capacitor is 0.
Look at my figure for the 4 surfaces.
I have charges on these surfaces as q1,q2,q3 and q4.
Now you know that q1 +q2 =Q and q3+q4=0( As per the total charge on the plates).
Let's check field inside the conductor A.( Practically it acts as an infinitely long plate)
Field due to an infinite plate is q/2ε where q is the charge on the plate.
So field inside conductor A is
q1/2ε-q2/2ε-q3/2ε-q4/2ε=0.( Signs vary due to the direction)
Solving this equation with the first 2 equations also,
We get q1=Q/2, q2=Q/2
Similarly find the net field inside conductor B and equate it to 0.
You'll get q3=-Q/2 and q4=Q/2
Now if you look at my diagram, at any point between the 2 plates the net field due to surface 1 and 3 is 0!
So the entire system acts as if there are only 2 plates, both having charge of magnitude Q/2, but opposite sign, i.e they act like a capacitor!!
But the charge of the capacitor here is Q/2.

