Filament Lamp

A filament lamp is a type of light bulb that utilises a thin coil of wire, called the filament, to produce light.
The filament is usually made of tungsten, a metal with a very high melting point.
When electric current passes through the tungsten filament, it resists the flow of the electrons. This resistance leads to power dissipation in the form of heat.
As the filament heats up due to resistance, it begins to glow and give off light, a process known as incandescence.
The resistance of the filament changes with temperature: as the filament gets hotter, its resistance increases. This is a characteristic property of non-ohmic conductors.
The current-voltage graph of a filament lamp is not straight but curves. This is because the resistance of the bulb increases with voltage and, hence, higher the voltage, lower the current.
However, a downside of filament lamps is that most of the electrical energy input is converted into heat rather than light. This makes them relatively inefficient compared to other types of bulbs like LEDs or CFLs.
They also have a shorter lifespan as the high operating temperatures degrade the filament over time, eventually causing it to fail or ‘burn out’.

Understanding the working principle of a filament lamp is crucial to understanding concepts like resistance, heating effect of electric current, and the characteristics of non-ohmic conductors.