>>12125889Because voltage (charge) and current (the flow of charge) can’t change instantaneously. A capacitor accumulates charge. If you attempt to change the voltage across a capacitor, the slower you do that, the harder it will be, since the voltage across it prior has caused charge to accumulate, which will resist the attempted change. If you attempt to change the current through an inductor, the slower you do that, the faster you do that, the harder it will be, since the current through it prior is already a flow of charge, which now has to be resisted.
Power electronics utilize this non-instantaneous change in order to buck or boost voltage and currents.
A capacitor acts like an open to DC, holding a voltage across it, and a short for higher and higher frequencies AC, since charge doesn’t have a chance to accumulate.
An inductor acts like a short to DC, since it’s just a really long wire with current flowing through it, but is an open for higher and higher frequencies AC, since the current doesn’t have time to change.
Hope that helps!
