capacitors and inductors.... introductory articles.

here are several useful articles on capacitors inductors and how RC and LR circuits work.

the key is that these devices store energy for later use. capacitors store energy in electric fields and inductors store energy in magnetic fields.  they are short term storage devices unlike batteries which are long term devices.


you need to understand how these devices work to build filters.....


https://www.allaboutcircuits.com/textbook/direct-current/chpt-16/voltage-current-calculations/


http://www.electronics-tutorials.ws/capacitor/cap_8.html


http://www.electronics-tutorials.ws/rc/rc_1.html


https://www.electronicspoint.com/threads/smoothing-capacitor-vripple.271842/