22 October Potential Dividers (also known as Voltage dividers in the USA) part 1

On 25 October and in a later lesson we will be working on Potential Dividers. It is essential that you get a good understanding of these because:

• passive sensors are normally connected in a potential divider
• the resistance of the sensor changes in response to the environment (e.g. an LDR has a high resistance in the dark and a low resistance in the light)
• the change in resistance produces a change in the output voltage of the LDR

1)  The screenshot  below is from http://www.bbc.co.uk/schools/gcsebitesize/design/electronics/componentsrev4.shtml  which explains how to use a potential divider in an electronic circuit.  Please note that in electronics it's common practice not to show the power supply or battery - instead the diagram just shows a 'top rail' which would have the positive of the supply connected to it (V in) and a 'bottom rail' which is connected to 0 volts, the negative of the battery or supply.

2) The video below is a very good introduction to potential dividers - watch it and make notes for yourself.
http://www.youtube.com/watch?v=Mn2i3DPI-a4
 b



The video below includes some clear explanations - watch and add examples to your notes.  He mentions the concept of 'loading' the potential divider but the examples given only cover 'no load' situations - which are what you can expect to come across in AS physics ('loading' is putting a resistor across the output of the potential divider.   http://www.youtube.com/watch?v=u8pAGROJ5N4