A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light.

An electric current in
the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow. A fluorescent lamp
converts electrical energy into useful light much more efficiently than incandescent lamps. The typical luminous efficacy of fluorescent lighting systems is 50–100
lumens per watt, several times the efficacy of incandescent bulbs with comparable light output.
Fluorescent lamp fixtures are more costly than incandescent lamps because they require a ballast to regulate the current through the lamp, but the lower energy cost
typically offsets the higher initial cost. Compact fluorescent lamps are now available in the same popular sizes as incandescents and are used as an energy-
saving alternative in homes.
Because they contain mercury, many fluorescent lamps are classified as hazardous waste. The United States Environmental Protection Agency recommends that
fluorescent lamps be segregated from general waste for recycling or safe disposal, and some jurisdictions require recycling of them.[3]
Operation of pre-heat type fluorescent lamp The tube filaments, starter (glow switch), and ballast are all in series, which constitute a complete circuit once the
switch, is closed. As a current flow through, the gas (inert) inside the starter glows and the electrodes are heated. Since one of the electrodes is bi-metal, it bends
and makes contact with the other. At this instant, the circuit is metallically complete. The filaments of the fluorescent tube are then heated and partial ionization takes
place. The bi- in the starter cools and the contacts open. The magnetic field in the ballast collapses rapidly producing an inductive kick, which establishes a current
between the filaments and fires the tube into operation.
1. Cathode
o the positively charged electrode of an electrical device, such as a primary cell, that supplies current.

An electric arc,
or arc discharge, is an electrical breakdown of a gas that produces a prolonged electrical discharge. The current through a normally nonconductive medium such
as air produces a plasma; the plasma may produce visible ligh
Plasma is a state of matter in which an ionized gaseous substance becomes highly electrically conductive to the point that long-range electric and magnetic fields
dominate the behaviour of the matter. The plasma state can be contrasted with the other states: solid, liquid, and gas
mercury-vapor lamp is a gas discharge lamp that uses an electric arc through vaporized mercury to produce light.
A phosphor is a chemical compound that emits light when it is exposed to light of a different wavelength (i.e. color). Phosphors do not contain the chemical element
Phosphorus, which can be made to glow a different way
A terminal is the point at which a conductor from a component, device or network comes to an end.[1] Terminal may also refer to an electrical connector at this
endpoint, acting as the reusable interface to a conductor and creating a point where external circuits can be connected.[2][3] A terminal may simply be the end of a
wire or it may be fitted with a connector or fastener.[citation needed]
A canopy is an overhead roof or else a structure over which a fabric or metal covering is attached, able to provide shade or shelter from weather conditions such as
sun, hail, snow and rain

Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the
emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation

Krypton is mixed with argon in energy efficient fluorescent lamps, reducing the power consumption, but also reducing the light output and raising the
cost. Krypton costs about 100 times as much as argon.

The primary difference is in size; compact fluorescent bulbs are made in special shapes (which require special technologies) to fit in standard household light
sockets, like table lamps and ceiling fixtures. In addition, most compact fluorescent lamps have an "integral" ballast that is built into the light bulb, whereas most
fluorescent tubes require a separaThe primary difference is in size; compact fluorescent bulbs are made in special shapes (which require special technologies) to fit
in standard household light sockets, like table lamps and ceiling fixtures. In addition, most compact fluorescent lamps have an "integral" ballast that is built into the
light bulb, whereas most fluorescent tubes require a separate ballast independent of the bulb. Both types offer energy-efficient light.te ballast independent of the bulb.
Both types offer energy-efficient light.
Compact Fluorescent Lamps (CFLs)
CFLs combine the energy efficiency of fluorescent lighting with the convenience and popularity of incandescent fixtures. CFLs fit most fixtures designed for
incandescent bulbs and use about 75% less energy. Although CFLs cost a bit more than comparable incandescent bulbs , they last 6-15 times as long (6,000-15,000
hours).
CFLs work much like standard fluorescent lamps. They consist of two parts: a gas-filled tube, and a magnetic or electronic ballast. The gas in the tube glows with
ultraviolet light when electricity from the ballast flows through it. This in turn excites a white phosphor coating on the inside of the tube, which emits visible light
throughout the surface of the tube. Although CFLs are efficient and convenient to use, there are some challenges CFLs face and these include:

What are the Major Deficiencies in Fluorescent Lights:

Amongst the deficiencies in fluorescent lighting are the following:
 1. Fluorescent lights contain toxic mercury. Mercury as well as the phosphor inside the bulbs are hazardous materials that present a waste disposal
issue at the end of light’s life. Broken bulbs release a small amount of toxic mercury as a gas and the rest is contained in the glass itself.
2. Fluorescent lights age significantly if they are frequently switched on and off. Typical lamp life for a CFL is about 10,000 hours but this can degrade
as a consequence of frequent switching (turning on and off). Burning life is extended if lamps remain on continuously for long periods of time. It’s worth
thinking about in the event that you are using CFLs in conjunction with motion sensors that frequently activate and time out.
3. Fluorescent lights are omnidirectional. Omnidirectional lights produce light in 360 degrees. This is a large system inefficiency because at least half of
the light needs to be reflected and redirected to the desired area being illuminated. The need for reflection and redirection of light means that the output is
much less efficient for omnidirectional lights due to losses than it would be for the same light if it were directional by its nature. It also means that more
accessory parts are required in the light fixture itself in order to reflect or focus the luminous output of the bulb (thus increasing unit costs).
The ballast (resistor ballast) is a device for limiting the flow of sunlight and generating instantaneous high pressure. Following is some difference between the
electronic ballast and inductance ballast.
1. Inductance Ballast is an iron core inductance coil, the inductance characteristic is when the current changes in the coil, the magnetic flux changes,
resulting in the induction electromotive, its direction and current changes in the opposite direction, thus impeding the current changes. And usually used in
fluorescent lamps.
2. Electronic ballast, is one kind of ballast, refers to the use of electronic technology driven electric light source, so that to produce required electronic
equipment. Comparatively, is an inductive ballast (or ballast) Today fluorescent lamps more and more designed with electronic ballast, light and compact,
and even can be integrated with electronic ballast and lamp, at the same time, the electronic ballast can have both the functions of the Rev. So, the
individual Rev may be omitted.
3. Electronic ballast have much more features, such as improving the current frequency or current waveform (such as the use of a square wave) to improve
or eliminate the flicker phenomenon of the fluorescent lamp. Some disadvantages of the traditional inductive rectifier are being replaced by the growing
electronic ballast.
4.
Bimetallic corrosion can only occur when two dissimilar metals are in 'electrical' contact and are bridged by an electrically conductive liquid. The 'cell' produced can
result in corrosion to one of the paired metals.
A bimetallic strip is used to convert a temperature change into mechanical displacement. The strip consists of two strips of different metals which expand at different
rates as they are heated, usually steel and copper, or in some cases steel and brass. The strips are joined together throughout their length
by riveting, brazing or welding. The different expansions force the flat strip to bend one way if heated, and in the opposite direction if cooled below its initial
temperature. The metal with the higher coefficient of thermal expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled.

The Fluorescent Lamp

The greatest development in lighting since the 1879 incandescent

History (1938 first commercially available - Today)

Introduction & Statistics Ballasts

How They Work

Design Variations
Inventors and Developments Timeline
Fluorescents are a large family of light sources. There are three main types of fluorescent lamps: cold cathode, hot cathode, and electroluminescent. They all use
phosphors excited by electrons to create light. On this page we will discuss the cold and hot cathode lamps. Electroluminescent lamps use "fluorescence" but are so
different they are covered on another page. From this point when we refer to 'fluorescent lamp' we will be talking about a lamp with a glass discharge tube and
fluorescent coating on the inside, this is how the cold and hot cathode type of lamps are designed. Induction lamps are a form of fluorescent lamps but they don't
have electrodes. We have a separate page for them here.

The standard fluorescent lamp was developed for commercial use during the 1930's. The idea of the fluorescent lamp had been around since the 1880's however it
took steady work over the decades to finally create a working commercially viable model. This work was done by many, not one single inventor. See our inventors list
to learn more.

Common uses:
lamps both outdoor and indoor, backlight for LCD displays, decorative lighting and signs, both high bay and small area general lighting. Not used for lighting from afar
due to diffused nature of the light.

Advantages

-Energy efficient, so far the best light for interior lighting

-Low production cost (of tubes, not of the ballasts)
-Long life of tubes
-Good selection of desired color temperature (cool whites to warm whites)
-Diffused Light (good for general, even lighting, reducing harsh shadows)

Disadvantages

-Flicker of the high frequency can be irritating to humans (eye strain, headaches, migraines)
-Flicker of common fluorescent light looks poor on video, and creates an ugly greenish or yellow hue on camera
-Diffused Light (not good when you need a focused beam such as in a headlight or flashlight)
-Poorly/cheaply designed ballasts can create radio interference that disturbs other electronics
-Poorly/cheaply designed ballasts can create fires when they overheat
-There is a small amount of mercury in the tubes
-Irritating flicker at the end of the life cycle
1. How the Fluorescent Lamp Works

We discuss two types of fluorescent lamps: Hot Cathode, Cold Cathode

Simple Explanation Hot and Cold Cathode Lamps:
Fluorescent lamps work by ionizing mercury vapor in a glass tube. This causes electrons in the gas to emit photons at UV frequencies. The UV light is converted into
standard visible light using a phosphor coating on the inside of the tube.
1A. Hot Cathode 1B. Cold Cathode
1A. How it works: Hot Cathode
The most common fluorescent lamp is the hot cathode:
Parts:
This lamp consists of a glass tube filled with an inert gas (usually argon) at low pressure. On each side of the tube you will find a tungsten electrode. The ballast
regulates AC power to the electrodes. Older lamps used a starter to get the lamp going. Modern lamps use pulse start which is done by components within the
ballast.
How it works:Step by step explanation of a standard 4 foot long 40 watt straight tube lamps (this is the most popular size of fluorescent lamp in the world since the
1940s).
Note: There are two kinds of ballasts, the magnetic ballast which uses copper coils (transformers), and the electronic ballast. Electronic ballasts are favored today
because they use a lot less material and are lower cost to produce.
1.) AC electric current passes through the ballast. The ballast will step up 120 AC volts (in the US) to 216 V, next the power passed through a 'choke' or 'reactor', this
limits current and prevents the lamp from creating a type of short circuit which would destroy the lamp. All arc discharge lamps need a choke to limit current.
2.) The lamp's glass tube is called a discharge tube and it works by having electrons pass from one electrode to the other. This forms what is called an "arc". Getting
this started is a real challenge.
To get the lamp started you need a spike of high voltage to get the arc started. The colder the lamp is, the higher voltage you need to get a start. The voltage 'forces'
current through the argon gas. Gas has a resistance, the colder the gas, the higher the resistance, therefore you need a higher voltage with colder temperatures.
Since creating a high voltage is a challenge and dangerous, engineers figured out ways to 'preheat' the lamp, that way less of a high voltage is required. There are
different ways to start a lamp including: preheat, instant start, rapid start, quick start, semi-resonant start and programmed start. We will tell you about the main two
ways to make it start.
2a. Use a Starter (startswitch) - This method is the first and arguably the most reliable type of way to start a lamp according to some. Many facilities still have older
fixtures with startingswitch preheat fluorescents.
1.) In the early systems the starter contained a small neon or argon lamp. When the starter was cool at first, current ran through the starterswitch through the neon
lamp. The 1 W lamp would warm a bimetallic strip in the starter, while in the main arc tube the current passed through the tungsten electrodes which would make
them heat up and ionize some of the gas. This 'preheated' the lamp.
2.) Current passes through the tungsten electrodes on each end of the lamp. The electrodes are like a filament on an incandescent lamp, when current passes
through they heat up and give off free electrons. This process of letting off free electrons is called thermionic emission. The free electrons ionize the argon gas in the
tube. The first gas to be ionized is right around the filament, you can see it clearly in the photo above. An ionized gas is called a plasma.
3.) When the starter switch (with the little neon or argon lamp inside) gets warm enough, the bimetallic strip flips the other way, completes the circuit, bypassing the
small lamp. The lamp goes out and the entire circuit shorts. During the short the voltage falls to zero. The bimetallic strip cools and pops back open, opening the
circuit. In the ballast the transformer had a magnetic field, when the circuit is cut the magnetic field collapses and forms an 'inductive kick' from the ballast. Suddenly
this kick of high voltage is sent through the lamp and this starts the arc. If it didn't work, if the lamp is still too cold, then the starter switch will light again and repeat
the process.
2b. Rapid Start - This modern type of starting method constantly preheats the electrode (cathode) using low voltage AC power. The arc is started by passing through
a grounded reflector or starting strip on the outside of the glass tube. The arc starts between the electrode and the starting strip first and rapidly propagates through
the entire discharge tube. The schematic for this and other modern start methods is much more complex.

3.) So now your arc has started and current passes from your cathode to your anode (electrode to electrode) through the argon gas. Because your dealing with AC
power, the cathode switches back and forth. AC power is good for the lamp because if the lamp was DC, the cathode side would be brighter and more intense since
there are more free electrons spewing off of the tungsten electrode there. Also if the lamp was on DC power, the electrode which is acting as the cathode would
become weaker as it lost tungsten atoms and the lamp would not last as long. Since we use AC the electrons or ions break off one side, reach the other, then on the
next cycle are sent back. Also the lamp tube has a nice uniform brightness on both ends.
Powdered phosphors on the inside of the tube absorb the UV light. Here you can see the UV light as a purplish light. The quartz lamp used in this experiment is the
same as a compact fluorescent lamp except that it has no phosphor.
4.) Vaporizing mercury and making light: The normal fluorescent lamp has a small amount of mercury in the tube. On a cold tube you would see it as a couple of
pinhead sized dots if you were to break the tube so you can see inside. The arc which started in argon gas quickly warms up the mercury liquid stuck to the side of
the tube. The mercury boils or vaporizes into the arc stream. The arc easily passes through vaporized mercury. This creates UV light. That light is emitted and strikes
the phosphors on the inside of the glass tube. The phosphors convert the light into useful visible light.
Phosphors are chemically designed to give off a certain color. Here you see a warm white at 3000 Kelvin (color temperature) and cool white which is closer to
daylight at 6000 Kelvin
1. Filament electrodes are preheated and glow red
2. The Cathode begins to ionize argon gas surrounding it
3. This lamp is powered by AC power, so the cathode switches to the other side and you see the left side begin to ionize, the other side (now the anode) stays warm
and ionized
4. The left side cathode warms to full and both sides are warmed up
5. The ballast provides a high voltage kick which instantly ionizes the entire tube to a high level of brightness
6. The lamp returns to normal voltage and its warmth has vaporized all the mercury, the lamp operates as normal
More on the Science:
Why does electricity flow through the gas? In a solid metal wire electrons jump freely from atom to atom, while the atoms stand stationary. In a gas there are also free
electrons "jumping" their way from the negative electrode to the positive at the other side. What is different is that you also have ions moving as well.

What is an ion? An ion is an atom with positive or negative charge. If an atom has one extra, or one less electron than normal, it will have a + or - charge. In an
ionized gas the negative ions will flow/move towards the positive electrode.
How do you get gas ionized? Normally you could not send current through a gas, but if you introduce free electrons and ions into the glass tube you can ionize the
gas. This is done by have a filament electrode, current heats up the filament which boils off electrons into the tube, this ionizes the gas
Ballast
Watch the video above to learn the basics about different types of ballasts.
Ballasts are a fascinating part of the fluorescent lamp system due to the complex nature of resistance, inductance and reactance. There are two kinds of ballasts: the
magnetic ballast, and the electronic ballast
Magnetic Ballasts: magnetic ballasts use transformers to convert and control electricity. Understanding the ballast takes some background because it uses the
complex property of induction The ballast raises voltage, but the most important thing is that is limits current.
Why do we need a ballast?
As current forms an arc through the lamp, it ionizes a higher percent of gas molecules. The more molecules are ionized, the lower the resistance of the gas. We know
that no resistance will equal a short. So without the ballast to control the current, current would rise so high that the lamp would melt and destroy itself.
How it works: the Magnetic Ballast
The transformer which is called a "choke" in a ballast is a coil of wire called an inductor. It creates a magnetic field. The more current you put through, the bigger the
magnetic field, however the larger magnetic field opposes change in current flow. This slows the current growth. Since we are dealing with AC power, the current
flows in one direction for only 1/60th or 1/50th of a second, then drops to zero before flowing in the opposite direction. Therefore the transformer only has to slow
current flow for a moment.
Weaknesses: The magnetic ballast operates at lower frequencies than an electronic ballast, it also rarely can fail and drip hot tar. Tar is used to insulate the
transformers in the ballast and reduce the humming noise. Some older fixtures have a capacitor with PCBs inside, but it is a very small amount, about one teaspoon.
Equally electronic ballasts have phenol, arsenic and their own set of contaminants.
Left: Historic ballasts galore at the Edison Tech Center's storage building
Above: electronic ballast in a CFL
Electronic Ballasts: The electronic ballasts use semiconductors to limit power to a fluorescent lamp. First the ballast rectifies the AC power, then it chops it to make a
high frequency for improved efficiency. The ballast can more precisely control power than a magnetic ballast but does have a number of problems
The design is quite different for each lamp. Some lamps only need a simple resistor to control power. LEDs need a low power resistor for current control. The resistor
is not acceptable for larger power lamps because it creates a lot of waste heat and therefore reduces efficiency. Electronic ballasts usually change the frequency of
power to a lamp from 50/60 Hz to 20kHz+.
Electronic ballasts are usually viewed as being more efficient because by running a lamp at a higher frequency you get more efficacy or brightness from the lamp
above 10kHz. This is in theory, however poorly or cheaply constructed ballasts will ruin the advantage of the electronic ballast. Most electronic ballasts are cheaply
constructed in China.
Manufacturers use as little copper and other expensive materials as possible. Components have less ability to deal with heat and rigors of long life. Regular
fluorescent lamps (discharge tube assemblies) have the ability to be highly efficient, but poorly made ballasts are the limiting factor. Electronic ballasts also have a
way of failing prematurely due to overheating and this limits the great life of the lamp. The stated life of a lamp on the box usually is not to be believed.
1B. How it works: Cold Cathode Fluorescent Lamps
The Cold Cathode Lamp is different from a Hot Cathode in that it has an interior coating that more easily creates free electrons when used with higher voltages.
The Cold Cathode device was not born as a light source. It is an evacuated tube filled with gas with an electrode at each end. The earliest cold cathode tubes
included the Geissler tube (1857) which was used for science and entertainment (provided an amusing glow depending on the gas within). Over the years cold
cathode tubes were developed to perform a variety of functions including counting, voltage regulation, radio detection, phase angle control in AC, computer memory,
radio frequency transmission, high voltage control switches, and more. Early devices were called: the Geissler Tube, Plucker Tube, Cathode Ray Tube, thyratron,
krytron, and dekatron.
Cold Cathode Lamps
Neon Lamps and Cold Cathode Fluorescent Lamps (CCFLs) create light as their primary function. Neon Lamp is a term describing lamps with a tube smaller than 15
mm in diameter.
Applications of CCFLs:
-Back lighting for LCD screens
-Computer monitors (tube)
-Television Screens (LCD, CRT)
-Alcove lighting and background diffused indirect lighting
-Nixie Tubes - early form of numeric display, they are small glass tubes shaped as numbers, activated by a wire mesh anode and multiple cathodes, replaced by
LEDs in the 1970s