Why do the lists of materials and schemes always recommend 16 V or 25 V capacitors in circuits that are fed by only 12 V and even less? Would not be right that the capacitors have the same voltage as the circuits?
The voltage of a capacitor is not the one in which it must operate in a circuit. The voltage marked on a capacitor is the maximum voltage that it supports without damaging, ie, without its dielectric ruptures burning it. Thus, it is good practice to always use a capacitor of higher voltage from the one in which the circuit where it is. For example, a source of 12 V, the peak voltage after rectification can reach 16 V, thereby, it is recommended that the capacitors are of 16 V or more. A good recommendation is to always use a capacitor in a circuit with an operating voltage at least 50% greater than that one we find in the maximum circuit.