Electric resistance is a property of a material that determines its ability to resist the flow of electric current. It is measured in ohms and is denoted by the symbol "R". The resistance of a material depends on its intrinsic properties such as its length, cross-sectional area, and resistivity.

What is Electric Resistance?
Electric resistance is the opposition encountered by the electric current when it flows through a conductor. It is similar to the concept of friction in mechanical systems. The flow of current is impeded by the collisions between the free electrons and the atoms in the conductor.

Ohm's Law and Resistance
According to Ohm's law, the current passing through a conductor is directly proportional to the voltage applied across it and inversely proportional to the resistance of the conductor. Mathematically, it can be expressed as I = V/R, where I is the current, V is the voltage, and R is the resistance.

Electric Bulb and Resistance
An electric bulb utilizes the concept of resistance to produce light. Inside the bulb, there is a filament made of a material with high resistance, usually tungsten. When an electric current passes through the filament, it encounters resistance, causing the filament to heat up and emit light.

Incandescent Bulbs
In traditional incandescent bulbs, the filament is heated to a high temperature by the electric current. As the temperature increases, the filament starts to glow and emits visible light. The high resistance of the filament allows it to heat up quickly, converting electrical energy into thermal energy and light.

Halogen Bulbs
Halogen bulbs are an improved version of incandescent bulbs. They also have a filament made of tungsten, but the bulb is filled with a halogen gas. The halogen gas prevents the filament from evaporating, allowing the bulb to last longer. The high resistance of the filament still causes it to heat up and emit light.

LED Bulbs
In contrast to incandescent and halogen bulbs, LED (Light Emitting Diode) bulbs do not rely on resistance to produce light. LEDs are semiconductors that emit light when a current passes through them. They are highly efficient and have a longer lifespan compared to traditional bulbs.

Conclusion
Electric resistance is a fundamental property of materials that determines their ability to impede the flow of electric current. It is utilized in various types of electric bulbs, such as incandescent and halogen bulbs, where the resistance of the filament causes it to heat up and emit light. LED bulbs, on the other hand, use a different mechanism to produce light and are more energy-efficient.