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 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