Potential Dividers Flashcards
What is a potential divider?
consists of at least two resistors in series, with a source of fixed potential difference
the potential difference of the source is divided between the components, as they are in series
What are the uses of a pd divider?
supply a pd which is fixed at any value between zero and the source pd
to supply a variable pd
to supply a pd that varies with physical condition such as temperature or pressure
How is pd across a resistor calculated in a potential divider?
V1 = IR1 = V0R1 / R1 + R2…
What does the equation V1 / V2 = R1 / R2 show?
the ratio of the pds across each resistor is equal to the resistance ratio of the two resistors
How can a variable pd be supplied?
source pd is connected to a fixed length of uniform resistance wire
a sliding contact on the wire can then be moved along the wire
giving a variable pd between the contact and the end of the wire
a uniform track of suitable material may used instead of resistance wire
What are the uses of a variable potential divider?
audio volume control to change volume of the speaker
vary the brightness of a bulb
What are sensor circuits?
produces an output pd which changes as a result of a physical variable
How does a temperature sensor work?
it consists of a potential divider using a thermistor and a variable resistor
if the temperature is raised, the resistance falls and the pd across it falls
How does a light sensor work?
uses an LDR and a variable resistor
pd across the LDR changes when the incident light intensity changes
if the light intensity increases, the resistance of the LDR falls and the pd across the LDR falls
