A dimmer, or dimmer switch, is a device that is used to regulate the amount of power dispersed to a light to control its brightness. A dimmer can be controlled manually or by remote control, to adjust the level of the lighting in a room. Dimmers are often used to conserve electricity in order to keep power costs down, and they are also used for mood or task lighting. A low level of light creates a nice relaxing atmosphere, while brighter light is necessary for activities like reading. With the touch of a switch or a knob, a dimmer can be adjusted to just the right setting.

But how does a dimmer work? A simple explanation is that the power current is cut back by the switch, allowing only a certain amount of current to reach the light. The strength of the current that moves through the filament in the light bulb determines the amount of light given off by the bulb. This amount of current is determined by the various settings a particular dimmer switch provides. A dimmer may have a switch plate with a switch that slides up and down to adjust the lighting. The settings may be numbered or shown as high, medium, and low.

Another type of dimmer utilizes a knob that is turned clockwise to increase the level of light, and counterclockwise to dim the light. The settings may be marked and a tiny click may be heard as the knob is set to another level, or the knob may move smoothly through the different settings until the desired level of dimness or brightness is achieved. A digital dimmer uses a microprocessor, tends to be less expensive, and is generally considered more reliable than other options.

Aside from the types of dimmers used for residential or commercial lighting, vehicles also include a dimmer switch for headlights. Depending on the make and model of the vehicle, there may be several light settings, or the dimmer may be limited to differentiating between standard headlights and a bright setting.