Hi PF. This isn't really a homework question so I posted it here. We were supposed to find a list of devices which we found used capacitors for homework but I had some questions about the capacitors I found in an old Del PC. I have attached the picture to this thread. There seems to be a large collection of big capacitors (2200 microfarads) on the left side of the picture which have near them these green circles with coils wrapped aorund them. What are these green circles and what is the role of these specific capacitors in the computer? I have a basic understanding of capacitors e.g. exponential decay, time constant, dielectrics, touched on displacement current and we have looked at some of the uses of capacitors (smooth lumpy dc voltage, provide quick bursts of energy, block dc component of ac current). Many thanks for any help offered.