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A lighting ballast is a piece of equipment required to control the starting and operating voltages of electrical gas discharge lights. Examples of gas discharge light sources include fluorescent and neon lights and high-intensity discharge (HID) lamps. The term lighting ballast can refer to any component of the circuit intended to limit the flow of current through the light, from a single resistor to more complex devices. The lighting ballast is necessary to operate discharge lights because they have negative resistance, meaning they are unable to regulate the amount of current that passes through them. A lighting ballast must be used to control current flow; otherwise the light could fail. Small light sources can use passive components, which require no additional power to operate, as ballasts. An example would be a series resistor that limits the flow of current across its terminals. For high-powered lights, however, a resistor would waste a large amount of electricity, so a more complex lighting ballast is required. |