Definition – An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated to a high temperature, by passing an electric current through it, until it glows with visible light (incandescence).

Working Principal –

A bulb consists of a glass housing which is filled with inert gas, two lead in-wires which are connected with a filament. When we switch on electricity, the current passes through the lead in wires & reaches filament which is made of Tungsten. Tungsten has very high melting point i.e. 2482° C). Now filament will heat up so much that it’ll glow red or white hot and give off light. The tungsten is very thin and is used in coil form which offers maximize resistance in the wire. When electricity passes through the filament, it gets heated up &glow.

The tungsten is placed in the glass housing for two reasons – 1) It protects people from hot filament and 2) it also keeps oxygen away from the hot metal, which would make it immediately burn up.

The bulb is usually filled with a low pressure, inert gas such as argon. The function of argon is to stop the oxygen in the light bulbs from corroding the hot tungsten filament. The use of argon in light bulbs prevents the evaporation of the tungsten filaments, which results in increased light bulb life.

Disadvantage of incandescent bulbs- As almost all electricity fed to bulb is converted into heat, therefore, energy consumption is high in such bulbs (almost 80% energy wasted in heat generation).

RANGE OF INCANDESCEND BULBS –

Range of bulbs–5W, 25W, 40W, 60W, 100W & 200W.These bulbs are available in different – different colors such as clear, milky, red, yellow etc. Such bulbs are fixed in a holder. These holders are available in various designs.

(Note– These days such bulbs are being used in very limited area due to high power consumption. Such bulbs have been replaced by CFLs & LEDs)

BULB HOLDERS –

Holders are also available in different shapes & sizes. Mostly, two types of holders are available in market – pin type & thread type. Pin type holders are standard holders while thread type holders are available in different threads e.g. E10(Mini Screw), E11(Mini Candelabra), E12(Candelabra),E14(European),E17(Intermediate),E26 (Mediam), E27(Mediam),E39(Mogul), E40(Mogul),EX39(Extended Mogul).

Frequently Asked Questions (FAQs) on Incandescent Bulbs –

Q1) Who invented Incandescent bulb?

Ans) Thomas Edison invented Incandescent bulb. He practically developed incandescent bulb in 1878 & filed his patent on “improvement in electric lights” on 14^th Oct, 1878. But he continued his experiment on this product where focus was on filament to improve the performance of bulb & finally Thomas Edison & his team discovered that carbonized bamboo filament could be used for 1200 hrs. Then in 1880, they started promoting its product for commercial use.

Q2) How many lumens in a 60W bulb?

Ans) The average lumens per watt for incandescent bulb is 15 lm/w for rough calculations, therefore a 60 watt bulb will have 900 Lumens (15*60).

Q3) Explain how Incandescent bulb produce more heat as compared to fluorescent? Also which light is more efficient incandescent bulb or fluorescent tube?

Ans) An incandescent bulb produces more heat because in this bulb light is produced when filament is heated up. Aprox 80% of energy is used in heat generation that is why this bulb is very energy inefficient & produce heat also. On the other hand fluorescent bulb use electricity to produce arc between two end s of the tube which makes the phosphor coating to produce light. In this process generate very less heat & improve efficiency of fluorescent bulb.

Q4) An Incandescent bulb gives what kind of visible spectrum?

Ans) The incandescent bulbs emit light of continuous spectrum or linear spectrum which means that all visible colours are present. No ultraviolet light is emitted by Incandescent bulbs. They emit light between 2800 K to 3200 K in colour temperature.

Q5) Which gas is commonly filled in an incandescent bulb? Or Why is inert gas used in Incandescent bulb?

Ans) An inert gas such as argon is used in incandescent bulb. The function of argon is to stop the oxygen in the light bulbs from corroding the hot tungsten filament. The use of argon in light bulbs prevents the evaporation of the tungsten filaments, which results in increased light bulb life.

Q6) What is the difference between Incandescent bulb & CFL?

Ans) An incandescent light bulb emits light by heating up filament when electric current passes through it. Almost 80% of electricity is used for heating up the filament & rest 20% energy is converted into light That is why these incandescent bulbs make their surroundings very hot.

On the other hand, in CFL (Compact Fluorescent Lamp) the glass tube is bent & both ends are fixed on to the base where ballast is fixed. When the lamp is switched on, a component called the ballast produces a high voltage between the electrodes, which is necessary for the initial ionization of the gas in the tube. Once the lamp starts operating, the current and light output can be maintained using a much lower voltage. In this process less heat is produced & consume less energy as compared to incandescent bulb.

 

Q7) LED Vs Incandescent bulb?

Ans) An incandescent light bulb emits light by heating up filament when electric current passes through it. Almost 80% of electricity is used for heating up the filament & rest 20% energy is converted into light That is why these incandescent bulbs make their surroundings very hot.

On the other hand, LED (Light Emitting Diode) is a p–n junction diode (a semiconductor material), which emits light when activated. When a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. It’s a solid state device and doesn’t require heating of a filament to create light. LEDs are not bulbs or lamps in the true sense. To make it usable as bulb are placed on a circuit board or other material that allows electricity to pass through at a specific voltage and current and with components required to operate them at specific voltages.

Q8) What is power factor of Incandescent bulb?

Ans) Power factor of Incandescent bulb is 1 or unity because it’s purely a resistive load, therefore no lagging & leading problem between voltage & current.