A light bulb in a circuit serves as a load that converts electrical energy into light and heat.
When an electric current flows through the filament of the bulb, it heats up due to electrical resistance. As the filament heats up, it reaches a temperature high enough to emit visible light. This process is a clear demonstration of how electrical energy can be transformed into other forms of energy.
In practical terms, the light bulb provides illumination, allowing us to see in dark environments. It is a crucial component of many electrical circuits, acting as an indicator that electricity is flowing through the circuit. If the bulb is lit, it shows that the circuit is complete and the electrical current is working as intended.