Filament lamps

A circle with a cross inside, centred on a horizontal line.Lamp

A filament lamp is a common type of light bulb. It contains a thin coil of wire called the filament. This heats up when an electric current passes through it, and produces light as a result.

The resistance of a lamp increases as the temperature of its filament increases. The current flowing through a filament lamp is not directly proportional to the voltage across it.

This is the graph of current against potential difference for a filament lamp:

A graph with current on the y axis and potential difference on the x axis for a filament lamp. A curved line goes through the graph at 45 degrees.