Why do Clock-radios get static in volume slider?
It's because some consumer devices are built down to a price and as such usually use the cheapest components available. In the case of a clock radio's volume it's the rotary thumbwheel potentiometer behind the volume control. A little bit of contact cleaner (electrical, not optical) will improve the situation, but at the end of the day the pot is a piece of garbage that just won't last a long time.