CIE IGCSE Physics

Revision Notes

4.2.10 IV Graphs

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Current & Potential Difference

  • As the potential difference (voltage) across a component is increased, the current in the component also increases
  • The precise relationship between voltage and current can be different for different types of components and is shown by an IV graph:

IV graphs, IGCSE & GCSE Physics revision notes

IV graphs for a resistor and a filament lamp

  • The IV graph for a resistor is very simple:
    The current is proportional to the potential difference
  • This is because the resistor has a constant resistance

 

  • For a lamp the relationship is more complicated:
    The current increases at a proportionally slower rate than the potential difference
  • This is because:
    • The current causes the filament in the lamp to heat up
    • As the filament gets hot its resistance increases
    • This opposes the current, causing it to increase at a slower rate

 

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