non-polarized capacitors
P-C has a small size with the large capacitance, is used only in DC circuits or circuits related to DC current.
P-C has a large leakage current, low frequency response - only up to about tens of kHz at aluminum or 1MHz at tantalium caps.
NP-C has a big size with the smaller capacitance, is used both in DC or AC circuits, low or high frequencies.
NP-C has a very small leakage current, high frequency response - up to hundreds of GHz up to types.
In general, they cannot replace for each other.
Sometimes, in household appliance in frequency of 50/60Hz, they can use 2 P-C caps (with capacitance doubled of the NP-C) connected in series by opposite terminals (and diodes in parallel with each cap to protect it from reversed voltage) to replace 1 NP-C cap to save space, but this type of replacement is not strongly recommended.
nguyennam