Minecraft wiki entry for Redstone_mechanics, associated text: Redstone components and blocks may or may not be powered. A "powered block" can be thought of as a block that has electricity running through it. Some blocks will show their powered state visibly (for example, redstone dust lights up, a redstone lamp illuminates its surroundings and a redstone torch turns off), but other blocks may give no visual indication of their powered state other than their effect on other redstone components.