In an electric bulb, a metal is heated to high temperatures using electrical energy so as to emit visible light. Since high temperatures are involved, electric bulbs are manufactured with tungsten filaments as tungsten has a very high melting point (3422 degreeC). However, producing light by heating tungsten filament is highly inefficient as most of the energy is emitted as infrared light and the only small portion of input energy is converted into the visible light.

How a Bulb Glows

Introduction:
A bulb is an electrical device that produces light when an electric current passes through it. It consists of a filament enclosed in a glass bulb, which is filled with an inert gas such as argon or nitrogen. When the filament is heated by the flow of electric current, it emits light.

The Filament:
- The filament is the thin wire inside the bulb made of tungsten, a metal with a high melting point.
- Tungsten is used because it can withstand the high temperatures required for light production.
- The filament is coiled to increase its surface area, allowing it to produce more light.

Electric Current Flow:
- When a bulb is connected to a power source, such as a battery or electrical outlet, an electric current flows through the filament.
- The electric current is the flow of electric charges, typically electrons, through a conductive material like the filament.
- The current flows from the positive terminal of the power source, through the filament, and returns to the negative terminal.

Resistance and Heating:
- As the electric current flows through the filament, it encounters resistance.
- Resistance is the opposition to the flow of electric current and is a property of the filament material.
- The resistance causes the filament to heat up, as electrical energy is converted into heat energy.
- The heating of the filament is what makes it glow and produce light.

Incandescence:
- The high temperature of the filament causes it to emit light through a process called incandescence.
- Incandescence is the emission of visible light as a result of being heated to a high temperature.
- As the filament gets hotter, it starts to emit light in the visible spectrum, producing the characteristic glow of a bulb.

Inert Gas Filling:
- The glass bulb of the bulb is filled with an inert gas, such as argon or nitrogen.
- The inert gas helps to prevent the filament from oxidizing and burning out quickly.
- It also allows the filament to operate at a higher temperature, producing a brighter light.

Conclusion:
When an electric current passes through the filament of a bulb, it heats up and emits light through incandescence. The resistance encountered by the current causes the filament to heat, and the inert gas filling the bulb helps to maintain the filament's temperature and prolong its lifespan. The combination of these factors allows a bulb to glow and produce light.

Electricity flows through a thin wire in the light bulb called the filament. ... Therefore as a result of this, the filament heats up and starts glowing, converting electrical energy to light energy. This is because of the Joule-effect, which means that resistances heat up when electrical current runs through them.