5 Different Fluorescent Tube Sizes and How to Choose One

Fluorescent light tubes are glass lamps that produce light through a unique action of ionized mercury atom causing a powdered phosphor coating inside the bulb to glow (fluoresce). Although LED (light-emitting diode) light bulbs are increasingly popular and have largely replaced standard incandescent light bulbs in residential applications, tube-like fluorescent bulbs (lamps) and fixtures are still popular in some applications, due to their low energy consumption and the quality of the diffused light they emit. Fluorescent light fixtures using long tube-shaped lamps are often used for workshop and hobby lighting, for example. A 4-foot-long fluorescent tube over a workbench can be much more effective than standard incandescent or LED bulbs in traditional light fixtures. Fluorescent lighting can also work well for providing supplemental light for growing plants, or for needle-crafters and other hobbyists.

And there are also screw-in forms of fluorescent lamps that fit the sockets on standard light fixtures and in floor and table lamps. Known as CFL (compact fluorescent light) bulbs, they were regarded as an excellent energy-saving alternative to incandescent bulbs—at least until the advent of LED technology.


One very legitimate reason why the use of fluorescent bulbs is waning, in favor of increased use of LED bulbs, is that fluorescent bulbs contain a small amount of hazardous mercury. This makes fluorescent bulbs difficult to dispose of safely. Always consult your local waste management agency for advice on what to do with burned-out fluorescent bulbs. Another reason to avoid fluorescent lighting is that LEDs are more cost-effective over the long run. Though more expensive initially, LED bulbs generally last much longer than fluorescent tubes, making them a better long-term bargain.

Fluorescent tubes (officially known as “lamps”) come in five basic types, identified as T2, T5, T5HO, T8, and T12, and The “T” designation stands for “tubular,” and the following number refers to its diameter in 1/8-inch diameter increments. A T12 bulb, for example, is 12/8 inch in diameter, or 1 1/2 inches. A T2 bulb, on the other hand, is 2/8, or 1/4 inch, in diameter.

Here’s what you should know about each basic fluorescent tube size.

What Is a Fluorescent Light Tube?

All fluorescent tubes (lamps) consist of a sealed glass vessel that contains a small amount of mercury and an inert gas, usually argon, at a very low pressure. The inside of the tube or bulb is coated with phosphor powder. When the light fixture is turned on, electrodes inside the tube or bulb ionizes the mercury vapor, which causes light to be emitted when the ionized atoms strike the phosphor coating lining the glass. This is a much different mechanism than that used by incandescent bulbs, which produce light when an inner metal filament gets hot enough to glow from the electricity passing through it. And it is also different than LED bulbs, which produce light from electrical current passing through microchips.

Fluorescent Tubes vs. Fluorescent Bulbs

In a fluorescent tube, there is an electrode at either end of the tube. A device known as a ballast steps up the 120-volt line current in the circuit to a level sufficient to energize the mercury vapor within the tube. The electron flow moves from the electrode at one end of the tube to the electrode at the other tube, and light is produced as ionized mercury atoms strike the powdered phosphor that lines the inside of the tube.

A screw-in fluorescent light bulb is essentially a miniaturized version of the long bulbs used in shop lights and similar fixtures. In the bulb version, a miniaturized ballast is integrated into the base of the screw-in portion of the bulb. Most screw-in fluorescent bulbs consist of small T2 tubes tightly coiled together so that the bulb remains roughly the size of a standard incandescent light bulb.

Disclaimer: Curated and re-published here. We do not claim anything as we translated and re-published using google translator. All images and Tattoo Design ideas shared only for information purpose.

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