Caps smooth out voltage, but how about current? Is that what inductors are for?
For filter network uses in DC power supply, inductor blocking AC as much as it can and allow DC passing through, capacitor shorting away AC as much as it can and leave the DC untouched.
Best to look at vaccum tube power supplies where LC filtering (pi filter) was more common due to the practical size limits of the components operating on higher voltages before high value high voltage electrolytic capacitors were developed. Also look at filter decoupling networks in most car ICE equipment power supplies.
They can be used that way. But usually they are used as part of a tuned circuit in a RF application, like a radio.
There are many, many uses for inductors and capacitors. But your concern right now seems to be their uses in filtering a rectified ac Voltage sine wave (dc power supply). For dc power supply filtering purposes an Inductor connected in series with the dc power supply and the load basically serves the same purpose as a filter capacitor does when connected in parallel with the dc power supply. When connected in the above manner they both store energy during increases in the magnitude of the dc ripple Voltage and release that energy into the load during the decreases in the magnitude of the dc ripple Voltage. One of their many big differences is the capacitor's ability to store energy after the source for that energy is disconnected from the capacitor whereas an inductor absolutely must and always does immediately release all of it's stored energy when the source for that energy is disconnected from the inductor.
