How do florescent bulbs and ballasts work?

Answer 1

A ballast in a fluorescent lamp does two things: it steps up the voltage to drive the lamp, and it provides a "load" or operating resistance when the lamp "fires" and conducts. In a fluorescent application, the correct voltage for the lamp should be used, and the ballast supplies this by stepping up the line voltage. The ballast must also help with current limiting. When the gas in the fluorescent lamp ionizes and conducts, it basically forms a "short circuit" because the ionized gas presents a low resistance to the voltage source. But when the operationg current is routed through the ballast, the ballast is just basically stepping up the voltage until the lamp fires, and then when all the current tries to flow through the lamp, the windings in the ballast say, "Whoa, there, partner." This limits current. Remember that during both the positive and negative cycle of the sine wave that is driving the lamp, the lamp fires and the light comes on. For every cycle of line voltage, there are two "blinks" of the lamp.

Answer 2

No. The principle of incandescent lighting is that a current flows through a filament resulting in extreme heating of the filament and consequently light being emitted from the super heated filament. As the filament heats up, its electrical resistance increases and it does not need a ballast to limit the current.

A cold filament, as when a bulb is first turned on, has the lowest resistance and has the most current going through it. That is when a filament is most likely to burn out and when an incandescent bulb is most likely to fail.

Other Answer

Lighting requiring ballasts are commonly fluorescent and HID lighting. The purpose of the ballast is to provide a spike of current to trigger a chemical reaction in substances such as neon and such.

Answer 3

A small amount of Mercury vapor inside the tube supports an electrical arc which emits UV light. The chemical coating on the inside of the tube transforms the UV light to visible light.

The ballast is responsible for regulating the voltage and current in the electrical arc through the mercury vapor so that the bulb starts, maintains constant light, and does not damage itself or nearby objects.

Answer 2:

The entire theory of how florescent lights work is beyond the scope of this forum, but here's an overview.

Florescent bulbs have a small amount of mercury in vapor form in an inert gas such as argon all contained in a glass tube/bulb. This mercury vapor is heated to start the flow of electric current through it which causes the vapor to glow. But the current would run out of control if not regulated. The ballast regulates this current flow this flow of current to keep the current and amount of light constant. The mercury vapor is a quite efficient emitter of light but it is outside of our visual range (ultraviolet light), so the inside of the tube/bulb is coated with a powder that glows with visible light when the ultraviolet light strikes it. This glowing is called fluorescing thus the name florescent light.