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A fluorescent lamp is a glass tube containing some Mercury vapor, with a phosphorescent coating on the interior surface of the tube.
The mercury vapor is made to glow by using a high voltage across its electrodes that sets off an electric arc discharge in the tube. The discharge can also be described as a conducting plasma.
The resulting flow of current through the mercury vapor is stable and well-controlled by an external ballast, or loading device, which consists of a high-inductance choke-coil that is connected in series with the tube.
The continuing dischange glow is invisible to the human eye but it causes the phosphorescent coating on the interior surface of the tube to emit visible light.
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A fluorescent tube lamp works by using the fluorescence principle. It contains two filaments, one at each end of the tube, which glow to heat up the gas contained inside the tube.
The inner surface of the tube is coated with compound of elements having fluorescent properties, such as phosphorus. When it was manufactured all normal air was removed from the tube. In place of the air just a small trace of a gas is put into the tube, such as mercury vapor (for a white color), carbon dioxide (for green), neon (for red color), etc.
When the electrical supply is turned on, what happens is that the two filaments glow and then the contacts of the starter open. This action provides a voltage across the tube that is high enough to ionise the warmed-up gas inside the tube. This ionised gas, also called a "plasma", excites the special fluorescent coating on the inside of the tube so that it gives out visible light.
Note about the need for a choke and a starter
Without a high inductance choke in series with the tube, the plasma in the tube would simply short-out the service wires. That would always cause the circuit's protective fuse to blow - or its circuit breaker to trip - to cut off the supply of current to the tube. If that happened the tube light would never be able to perform its intended purpose, which is to continue running - and giving out a continuous light - for long periods of time.
The starter is a special kind of switch: its contacts are made of a metal alloy which, soon after a voltage is applied, heats up and bends, causing the switch contacts to open.
So a high-inductance choke must be used in circuit with the starter and the tube for two reasons:
- firstly the choke generates a high voltage pulse across the tube when the starter's contacts open. That pulse causes the gas in the tube to ionise and become a low-resistance plasma
and
- secondly, because it is wired in series with the tube, the choke greatly reduces the current drawn by the tube once it contains the low-resistance plasma.
For more information see the Related link below and the answers to the Related Questions.
What else can I help you with?
Why does the starter not strike after it has established the glow in the tube?
The starter does not strike after establishing the glow in the tube because it is designed to operate only during the initial phase of starting the fluorescent lamp. Once the gas in the tube ionizes and allows current to flow, the starter automatically disconnects from the circuit. This prevents it from interfering with the normal operation of the lamp, allowing the ballast to regulate the current and maintain the light output.
What types of capacitors are used in fluorescent tube starters?
electrostatic capacitor
What is the principle of electric tube light?
The way an electric tube, or fluorescent, light works is really very interesting. Most "regular" light bulbs are incandescent. Their source of light is the glow of electricity passing through a very thin wire known as a filament that is suspended in a vacuum. It glows with a "warm" color in the yellow/orange range. With a fluorescent tube there are two filaments, but they do not directly provide the light source, and a mercury vapor instead of a vacuum.On each end of a long glass tube are coils using electricity regulated by a ballast. The tube is filled with mercury vapor and phosphor. The electricity passing through the filaments excites the mercury vapor causing it to glow with ultraviolet (black) light. Ultraviolet light is not visible, but it does cause cause certain chemicals and colors to glow or fluoresce. If you take laundry detergent with phosphorous in it, for example, and place it under an ultraviolet (black) light, the phosphorus glows cold white. So by adding Phosphorus to the tube of Mercury vapor it will also glow when the vapor is excited electrically.The result is a lot of light for a much lower amount of electricity, and excess heat. The color temperature is very close to that of daylight but a little cooler, in the blue/green range. That makes growing plants under fluorescent light more effective also. The negatives are that most "tube lights" can not be dimmed with a wall dimmer-switch, and the ballasts, that controls electrical flow, do have a tendency to burn out or fail after a time.
How will you test starter and choke in fluorescent tube?
You can use a wire instead of the starter to test the tubes .. I did it, it works !
How choke coil limit current to the fluorescent tube?
A choke coil, also known as a ballast, limits the current to a fluorescent tube by providing a high impedance to the flow of current. This high impedance restricts the current flowing through the tube, allowing it to operate within its required current range. The choke coil also helps regulate the starting voltage and stabilize the operation of the tube.
What makes a fluorescent light glow?
A fluorescent light uses electricity to create ultraviolet light in a tube filled with mercury vapor and a phosphor coating. The ultraviolet light interacts with the phosphor coating, causing it to emit visible light, which is what makes the fluorescent light glow.
Lights that glow when an electric current causes ultraviolet waves to strike a coating inside a tube are called?
fluorescent lights
Why do fluorescent tubes glow red?
Fluorescent tubes typically produce white light when they are functioning properly. However, a red glow may occur if the phosphor coating inside the tube is damaged or if the tube is nearing the end of its lifespan. This can cause the phosphor to emit a reddish light instead of the normal white light.
Is fluorescent light produced by heat?
Fluorescent light is not produced by heat. It is produced when electricity passes through the mercury vapor in the fluorescent tube, causing the mercury atoms to emit ultraviolet light that then interacts with the phosphor coating inside the tube to produce visible light.
Why do fluroescent lights glow in the dark when swiched off?
A fluorescent tube contains (when operating) a plasma, and this excites phosphors coated on the inside of the tube. Some of these phosphors are phosphorescent, that is they will glow in the dark for a while due to being exposed to light. But that glow will soon cease. Other phosphors are fluorescent, that is they will glow only while excited. So the glow you observe is due to the phosphorescent particles in the coating, and they will soon diminish in brightness.
What are the positive points of ulteraviolet rays?
Ultraviolet rays can be used as for fluorescent lamps as certain chemicals glow when they absorb ultraviolet. In fluorescent lamps, the sindide of the tube is coated with a white powder that gives off light when it absorbs ultraviolet. The ultraviolet is produced by passing a current through a gas in the tube.
What are facts about mice?
mouse urine has a fluorescent glow....
Is einsteinium fluorescent?
Einsteinium produces a visible glow.
How does a fluorescent lamp operate?
A fluorescent lamp operates by sending electrical current through a gas-filled tube containing mercury vapor. This current excites the mercury atoms, causing them to emit ultraviolet light. The ultraviolet light then interacts with the phosphor coating on the inside of the tube, causing it to glow and emit visible light.
What helps produce light in fluorescent lights?
plasma
Do fluorescent markers glow under a black light?
Yes of course, that is why they are fluorescent.
What is a sentence for fluorescent?
The fluorescent light illuminated the room, casting a bright and vibrant glow over everything inside.
