A panel assembly includes a panel (10) having a light-pervious area (142), a light source (60) attached on the panel for lighting the light-pervious area, a variable resistor (30) electrically connected in series with the light source, and a rotating member (40) rotatably attached on the panel, the rotating member is engagingly coupled to the variable resistor and is manually rotatable in a manner that a resistance of the variable resistor is adjusted accordingly.