How does a capacitor work? I get how capacitor is made and the equation $Q=CV$ but I am trying to understand the principle behind it.
Is it reasonable to think that the reason a capacitor works is that each plate changes the potential of the other plate when placed closed by, so that the positive plate will increase the potential of the negative plate and vice versa so that you can put more charge on each plate than otherwise? 
 A: You are correct. There only is a certain amount of charge that can be given to a single plate because as charge is given its potential rises and beyond a certain limit the charges start leaking.
Now when you bring a second plate closer to let's to say a positively charged plate, the negative charges align on the face closer to the positive charge plate and the positive charges on the other face What this does is in fact reduce the potential of the positively charged plate and let you store more charge than you normally would have been able to
A: Consider you have one plate which is connected to wire.If you supply current through it then free electrons will move towards the plate making number of electrons greater than that of the proton on the plate so plate becomes negatively charged.But these electrons will be repell by each other again making plate neutral but if you bring another plate close to first plate then the electrons collected on the first plate will repell electrons from second plate so there will be more proton on second plate which attract the electrons of first plate and viceversa which make electrons stay easily on the first plate and electrons repell easily on next plate.In this way one plate get positively charged and next negatively charged other I hope you will understand yourself.
