I wonder why I cannot charge a capacitor with alternating current? Why can't I charge the capacitor with AC? How do the plates block the flow of electrons with DC but not with AC.
Somebody told me that the DC is blocked by the capacitor, so the capacitor gets charge, but I could not get the actual concept about it.
 A: Of course you can charge a capacitor with AC. The problem is that you keep changing how it is charged. While you apply a positive voltage to one plate, it will get a positive charge; half a cycle later, it will attempt to get a negative charge; and so it continues. The capacitor is always a little bit behind - as your AC voltage is changing, the capacitor gets rid of the charge it had before and tries to catch up with the charge you are trying to impose.
So - AC is not a good way to charge a capacitor: but any voltage (even AC) will change the charge on a capacitor - and so in essence "charges" it. But if you disconnect your AC voltage source at a given moment in time, the exact timing of the disconnection will determine what charge is left on the capacitor.
A: AC has each wire positive half the cycle and negative the other half.  It will charge the capacitor on one half cycle and discharge it on the other half.  The net charge will be zero. 
A: Too many explanations, few of them are: 


*

*$\\Z_c=\frac{1}{j\omega C}=\frac{1}{j0C}=\infty 
\\V_c=Z_cI=\infty $

*In DC, the voltage across the capacitance does not change after full charging and remains equal and opposite to the DC Voltage across it and hence no current can flow through it.
