Safe to install a resistor (of sorts) on a wall switch to force a light to dim?
Remember a resistor dissipates heat, if you have a 50 w bulb and want only 25 w of light a resistor would now be heating the area where it is connected also 25 w resistor would be fairly large and more expensive than A dimmer. A dimmer switch would be a safer and more energy efficient way to dim the bulb as the circuitry limits what part of the AC cycle is allowed to pass. So use a dimmer not a resistor.