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p3 (series (components connected in a line, current flows through all…
p3
series
components connected in a line, current flows through all components to get round the circuit
add cells in series, gives bigger pd because each charge gets a push eg two 1.5V in series supplies 3V
ammeters always in series, voltmeters in parallel
total pd of the supply is shared between various components
pds always add up to equal the pd across the power supply
total energy transferred to the charges in the circuit by the power supply equals total energy transferred from the charges to the components
current is the same everywhere, size of current determined by total pd of the power supply and the total resistance of the circuit
resistance adds up
resistance of two or more is bigger than just one because the battery as the push charge through all of them
bigger resistance, bigger share of total pd because more energy is transferred from the charge when moving through a large resistance than a small one
if resistance of one changes, pd across all components will change
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sensing circuits
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bigger resistance, more p.d it takes
as room gets hotter, thermistor resistance decreases and takes less pd
pd in the fixed resistor and fan rises, so fan goes faster
fixed resistor and fan always same p.d because in parallel
p.d of the power supply shared between the thermistor and the loop of the fixed resistor and the fan according to their resistances
or connect bulb in parallel to LDR, pd across both are high when dark, resistance in the LDR is high
bulb connected across an LDR gets brighter as the room gets darker
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parallel
all branches have the same pd, each charge can only pass down one branch of the circuit, must transfer all energy by the source pf of that branch
current shared between branches
total current going into a junction must equal the total current leaving
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investigate
in series, every time a bulb is added, pd falls as it must add to source pd, current falls as resistance is increased
bulb gets dimmer
in parallel, bulbs don't get dimmer
pd is equal to the source pd, no matter how many bulbs there are
current on each bulb is the same, and resistance of each branch stays the same
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diode
semiconductor eg silicon
lets current flow freely through it in one direction but not in the other, high resistance in reverse direction
use in radio receivers and for direct current in alternating supply
LDR
resistor dependent on light intensity
resistance high in darkness
as light increases resistance falls and the current increases
used for automatic night lights, outdoor lighting and burglar detectors
thermistor
resistance drops in heat
resistance increases in cold
if constant, curves as current increases, thermistor warms as resistance decreases
used in temperature detectors eg thermostats, irons and car engines
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charge gives up this energy when it falls through a potential drop in any components elsewhere in the circuit
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