Potential Divider

Physics: AQA A Level, topic 5.1.10

Potential dividers can be used to supply constant or variable potential differences from a power supply.

Often in electronics, the power supply has a potential difference that is too high for our intended use.
Another problem is that we might want a variable potential difference when we only have a constant potential difference power supply.
A potential divider circuit uses the resistance of a resistor to change the potential difference across a component.
When the second resistor has a high resistance, there is a reduction of the potential difference across the component.

If a variable resistor is now in place of R₁, the potential difference across the component can be altered.
When the variable resistor is set to zero, the component gets the full power supply of potential difference.
When the variable resistor is set higher, the component gets a smaller share of the full power supply of potential difference.
The potential difference can be altered to vary the potential difference with time or set it at a lower value than the power supply.

If a thermistor is now in place of R₁, the potential difference across the component is altered based on the temperature of the thermistor.
When the temperature is high, the thermistor resistance is close to zero and so the component gets nearly the full power supply of potential difference.
When the temperature is low, the component gets a smaller share of the full power supply of potential difference.

If a light dependent resistor (LDR) is now in place of R₁, the potential difference across the component is altered based on the light intensity incident on the LDR.
When the intensity is high, the LDR resistance is close to zero and so the component gets nearly the full power supply of potential difference.
When the intensity is low, the component gets a smaller share of the full power supply of potential difference.

Test yourself on Potential Divider