GCSE Physics (AQA)

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Filament Lamps

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Electricity Current, potential difference and resistance

Filament Lamps

3:31 Resistance of Circuit Components
Spec 4.2.1.4
Previous Ohmic Conductors Next Diodes
  • A filament lamp converts electrical energy to light.
  • Current flows through the filament wire in the bulb, causing it to heat up and glow.
  • Understanding the details of how lamps work is not necessary for exams, but recognizing and analyzing the IV graph is important.
  • The IV graph for a filament lamp is curved.
  • The IV graph shows the relationship between current (Y axis) and potential difference (X axis).
  • For a filament lamp, the graph is roughly straight in the middle for low potential differences and curves down at higher potential differences.
  • The pattern is the same when reversing the current to get negative values.
  • The filament lamp is a non-omic conductor, meaning current and potential difference are not proportional.
  • As current increases, resistance increases.
  • The gradient of an IV graph indicates the resistance of the component.
  • A steeper IV graph means lower resistance.
  • Near the origin, the lamp has a low resistance with a steep gradient.
  • At the ends of the graph, the lamp has high resistance with a nearly horizontal graph.
  • As potential difference increases, there is little change in current.
  • Resistance changes because larger currents increase the filament's temperature.
  • Higher current results in higher temperature and higher resistance in the filament.
  • The increase in resistance is caused by the increase in temperature.

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