I have a problem with knowing witch capacitor to use in a circuit because I am working on installing main circuit breaker where it is needed for 220 Volt AC current to be turned in to a lower current of 12 Volt useing a tramsformer. I would like to know how to calculate the capacity in farads without knowing the charge of the capacitor needed. The formula to calculate the capacitance of a capacitor Q=C/V would be more usefull in my opinion if I could know how to determine the charge of a capacitor.I want the AC current to be turned into DC current useing the right capacitor
To convert AC to DC, you will need a pn-junction (atleast two) which will allow for full-wave rectification of the current. This can be stabilized with the help of a capacitor in parallel or an inductor in series. The exact calculations depend on the specifications of the circuit.