13.5 The potential divider Flashcards
What does a potential divider consist of
Two or more resistors in series with each other and with a source of fixed potential difference.
By making a suitable choice of components, a potential divider can be used to:
Supply a pd which is fixed at any value between zero and the source pd
Supply a variable pd
Supply a pd that varies with a physical condition such as temperature or pressure
What does the equation V1/V2 = R1/R2 show
That the ratio of the pds across each resistor is equal to the resistance ratio of the two resistors.
Variable potential divider use - Loudspeaker
As a simple audio volume control
Change the loudness of the sound
Audio signal pd is supplied to the potential divider in place of a cell or battery.
Variable output pd from the potential divider is supplied to loudspeaker
Variable potential divider use - brightness of light bulb
Vary brightness between zero and normal brightness
Use of potential divider enables current through light bulb to be reduced to zero.
If variable resistor in series with light bulb used, there would be current through light bulb when variable resistor is at max. resistance
What does a sensor circuit do
Produces an output pd which changes as result of change of physical variable such as temperature or light intensity
What does a temperature sensor consist of
A potential divider made using a thermistor and a variable resistor
What does a light sensor use
A light-dependent resistor (LDR) and a variable resistor
pd across LDR changes when incident light intensity on LDR changes
What happens to the resistance of an LDR as light intensity increases
The resistance of the LDR falls and the pd across the LDR falls
