ELECTRIC LAMPS – PART – 01 – OPERATION OF INCANDESCENT AND GAS-FILLED LIGHT LAMP

INVENTOR OF INCANDESCENT LIGHT BULB

JOSEPH WILSON SWAN, British Physicist actually received the first patent for a complete incandescent light bulb with a carbon filament in 1878.  

SWAN’S HOUSE WAS THE FIRST IN THE WORLD TO BE LIT BY A LIGHT BULB.

EDISON AND SWAN merged their companies and together they were the first to design a bulb that was commercially viable in 1880.

SWAN'S original low-voltage, high-current bulb is still used in flashlights and automobiles.

INCANDESCENT - Emitting light as a result of being heated

INCANDESCENT LIGHT BULB is a source of light that works by incandescence, which is the emission of light caused by heating the filament.  

OPERATION

An incandescent bulb typically consists of a glass enclosure containing a tungsten filament. An electric current passes through the filament, heating it to a temperature that produces light.

MAJOR PARTS

1. Glass bulb                              2.Inert gas

3. Tungsten filament                  4. Contact wire (goes to foot)

5. Contact wire (goes to base)    6. Support wires

7. Glass mount/support              8. Base contact wire

9. Screw threads                        10. Insulation

11. Electrical foot contact

TYPES

1. CARBON FILAMENT LAMP

Melting point = 3500 degree centigrade

Working temperature = 1800 degree centigrade

Temperature coefficient = negative

Lamp efficacy = 2.5 to 4 lumen per watt

It gives yellowish light

At high temperature, it disintegrates and blackens the lamps inside surface.

2. TUNGESTEN FILAMENT LAMP

Melting point = 3400 degree centigrade

Working temperature = more than 2000 degree centigrade

Temperature coefficient = positive

Lamp efficacy = 14 lumen per watt.

It gives bluish-white light

TYPES OF FILAMENT LAMPS

(A) VACUUM TYPE LAMP

1. This type of lamps are perfectly evacuated. (Evacuate means create a vacuum in (a bulb, flask, reaction vessel).

2. Evacuation prevents oxidation of the filament material.

3. Evacuation results in vaporization of the filament material, which reduces its life.

4. Filament is wound in the shape of net.

5. Length of the filament of lamp is short.

6. Vacuum lamps are made of 10 to 25 watts.

7. At higher temperature the metal will start to disintegrate and the lamp will become defective.

8. This lamp produces less illumination.

(B) GAS-FILLED LAMPS

1. In order to raise the working temperature of a filament the bulbs are filled with an inert gas.

2. This lamps are used at higher wattage more than 100W.

3. A mixture of 80% argon and 20% nitrogen is an ideal combination.

4. Nitrogen reduces arcing between the filament turns.

5. Loss of heat by convection through gas is reduced by decreasing the surface area of the filament.

COILED COIL - FILAMENT

To make a 100W lamp about 300m of tungsten wire is needed.

Such a long wire cannot be accommodated in the small space of a lamp.

First the coil is coiled and is again recoiled; such a filament is called coiled coil filament.

CHARACTERISTICS OF INCANDESCENT LAMP AND DIMENSION OF THE FILAMENT - Please watch the video.

ADVANTAGES

1. Available in various shapes and sizes.

2. Not affected by surrounding temperature.

3. It operates at unity power factor.

4. Works well on either alternating or direct current.

5. They are also compatible with control devices such as dimmers, timers, photo sensors, and can be used both indoors and outdoors.

DISADVANTAGES

1. Low efficiency               

2. These lamps are very much sensitive to voltage changes.

3. The light output is white at higher voltages but the life of the filament reduces.