Incandescent Lamp also called Incandescent Bulb, is the most common type of artificial source of light used for indoor and outdoor lighting. They were widely used before CFL bulbs came into the picture. This post will discuss in detail, the meaning of Incandescent Lamp, how it works, parts of the Incandescent Bulb, and its Drawbacks.
What is an Incandescent Lamp
Light is produced in Incandescent Lamp when electricity runs through a thin wire called a Tungsten filament. The filament gets heated due to its high resistivity and converts electrical energy to visible light. The hotter the filament gets, the more efficient it is, in converting Electricity to Visible Light.
Fig. 1 – Introduction to Incandescent Lamp
Tungsten is an ideal choice due to its high melting point and low vaporization pressure. The length of Tungsten filament in the Incandescent lamp determines the Voltage of the lamp and the thickness of the filament determines the current consumption of the lamp.
Fig. 2 – Light Bulb Invented by (a) Joseph Swan (b) Thomas Alva Edison
Who Invented Incandescent Lamp – Joseph Swan or Thomas Edison
Rightfully the credit of inventing Incandescent Lamp should go to Joseph Swan as his experiments led to the discovery of practically usable light bulb. The bulbs in those times used Carbon Filament. Swan and Edison were involved in their studies of Incandescent Lamp and in the year 1850, Joseph Swan, physicist and chemist of England came up with a model which used Carbonized paper thread in an evacuated glass bulb.
In the year 1860, he was granted British Patent for his work. However, his model was unfit due to the poor quality of vacuum in the bulb which caused disintegration of Carbon. He later used Copper wires for the electrical supply and his bulb glowed for 13 and 1/2 hours. Joseph Swan started “The Swan Electric Light Company”, which produced commercial light bulbs in 1880.
On the other hand, Thomas Alva Edison in US worked on his version of an Incandescent Lamp. He patented his bulb in 1879, which was nothing but an improvisation of the design developed by Joseph Swan. He used a better Vacuum pump and instead of Carbon filament, he used filament derived from Bamboo and his bulb glowed for 1200 hrs. Modern day incandescent bulbs, which are made of Tungsten filament lasts for about 1,500 hours.
Fig. 3 – (a) Joseph Swan (b) Thomas Edison
Parts of Incandescent Bulb
It consists of several parts, namely;
- Glass Shell
- Tungsten Filament
- Contact Wire
- Stem
- Metal Base/ Cap
- Invisible Gases
Glass Shell
Glass Shell is the outer covering of the Bulb which you can touch and feel. When the bulb is switched ‘ON’ it gets extremely hot and you need to be cautious when it comes in contact with bare hands.
Tungsten Filament
The filament is made of Tungsten metal due to to its high melting point.
Contact Wire
Electrons or Electricity flows through the contact Wire or the connecting wires. They are connected to the base of the bulb. These wires complete the circuit.
Stem
The filament and the contact Wires need support so that they are intact. This support is termed as Stem which is made of glass.
Metal Base/ Cap
Metal Base/ Cap provide electrical contact to conduct Electricity.
Invisible Gases
Invisible gases are the inert gases which helps in preventing the filament from burning out. The stress on the Glass Shell is reduced which avoids glass breakage.
Fig. 4 – Parts of Incandescent Bulb
How does Incandescent Lamp Work
Let us consider a simple electrical circuit as shown in the Fig. 5. Electrons flow from the negative side of the Current Source to the conducting material from the base of the bulb. Electrons continue to flow through the wire inside and across the Tungsten Filament.
This causes conversion of Electrical energy to heat and light energy. The filament gets heated up rapidly and the presence of inert gases inside the bulb prevents the filament from burning out. The Electrons travel through another wire in the bulb to the other conductor on the base of the bulb to the positive side of the current source.
The Power ( Instantaneous Power) is given by the equation :
Fig. 5 – Representation of Closed Electrical Circuit
Disadvantages of Incandescent Lamp
The disadvantages are:
- It produces lot of heat and is impossible to touch with bare hands.
- It is very fragile and life of the bulb is short.
- Color range is limited.
Also Read: What is CFL - How it Works, Circuit Explanation, Advantages & Disadvantages Smart Street Light System: Architecture, Working Principle, Applications
