13.5 Potential divider Flashcards
what does a potential divider consist of
2 or more resistors in series with each other and with a source of fixed pd
what happens to the potential difference in a potential difference divider
the potential difference of the source is divided between the components in the circuit as they are in series with eachother
by making use of suitable choice of components how can a potential divider be used
to supply a pd which is fixed at any value between zero and the source of pd
to supply a variable pd
to supply a pd that varies with a physical such as temperature or pressure
current passing through 2 resistor in series =
I = pd across the resistors / total resistance
I = Vo / R1+R2
potential difference of one resistor in a potential divider
V1 = IR1 = VoR1/R1+R2
subsistute in R2 for the other resistor
what do the two pd equations show
that th pd across each resistor as a proportion of source of pd is the same as the resistance of the resistor in proportion to total resistance
v1/v2 =
r1/r2
this shows that the pds across each resistor is equal to the resistance ratio of the two resistors
how to supply a variable pd
the source is connected to a fixed length of uniform resistance wire.
A sliding contact can be moved along the wire giving a variable pd between the contact and one end of the wire
what can be used instead of resistance wire
a uniform track of suitable material
the track my be linear or circular
how can a variable potential divider be used to control audio volume and change the loudness of sound from a loud speaker
the audio signal pd is supplied to the potential divider in place of a cell or battery
the variable out put pd from the potential divider is supplied to the loudspeaker
how can a variable potential divider be used to vary the brightness of a light bulb between zero and normal brightness
use a variable resistor in series with the light bulb and source of pd
or
use a potential divider which enables the current through the light bulb to be reduced to zero
what happens if a variable resistor in series with a Leith bulb has been used
there would be a current through the light bulb when the varaiabkl resistor is at maximum resistance
what does a sensor circuit produce
an output pd that changes as a result of a change of a 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 happens when the temperature of he thermistor is constant
the sources pd is divided between the thermistor and the variable resistor
what happens when adjusting the variable resistor in series with the thermistor
the pd across the thermistor can be set at any desired value
when the temperature of the thermistor changes its resistance changes so the pd across It changes
what does a light sensor use
a light dependent resistor (LDR) and a variable resistor
when does the pd across the LDR change
when the incident light intensity on the LDR changes
if the light intensity increases the resistance of the LDR falls and the PD across the LDR falls
