Electronics often have things that hold a charge called capacitors. They’re like little pockets that hold energy temporarily and are normally periodically filled and drained and are used for all sorts of things. When you power something off, some of them can take several seconds to discharge. That whole time they might still be powering some part of the circuit preventing it from resting. Most electronic devices don’t require waiting 5-10 seconds, but it doesn’t hurt to take a few seconds to be sure
Latest Answers