Potential Dividers

A potential divider is usually some components like resistors, which are all in series with each other. There will be a supply voltage at the top which can be any suitable voltage, eg 12V, this will be the voltage which will travel around this potential divider until it reaches ground, which is 0V. The potential difference across the voltage supply is split in the ratio of the resistors in the circuit.

Example:

- If you had a 2 ohm resistor and a 3 ohm resistor, you would get 2/5 of the potential difference across the 2 ohm resistor and 3/5 across the 3 ohm resistor.

Also, by using the diagram above you can calculate the Vout by using this formula Vout = Vin x R2/Rt           - Vout = Voltage output                                                                                                                                      - Vin = Voltage input (Power supply, eg 12V)                                                                                                      - R2 = The resistance across the voltage you are wanting the calculate                                                          - Rt = The total resistance of the components in series with each other

Variable Resistor: You can replace one of the resistor in the circuit with a variable resistor. This will allow you to increase or decrease the resistance across the component. For example if you increased the resistance across the component, then because of V=IR then the voltage across the potential divider will increase meaning the voltage across the resistor in series will have a smaller voltage. This would be the opposite way around if you decreased the resistance across the potential divider.

LDR and NTC Thermistors: - A property that a LDR is that it has a very high resistance in the dark, but a lower resistance in the light.                                          - An NTC Thermistor has a high resistance at low temperatures, but a much lower resistance at high temperatures.

Any of these components can be used instead of a resistor in a potential divider so either the light level or temperature, depending on the component, will affect the voltage across that component and any other component which it is in series with.

Potentiometer: A potentiometer uses a variable resistor to give a variable voltage. If you had a length of wire connected to a power supply then if the wire is uniform then it's resistance is proportional to its length. This means that if you put a voltmeter across different lengths of the wire then the resistance would be proportional to the length, as you record across a larger length of wire then the resistance will be greater causing the potential difference to be bigger.