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Electrical circuits
P2 – part 2
Common components
What they do
Variable resistor – can change the resistance in a
circuit.
Diode – Only allows current to flow one way
(direction of the arrow)
LDR – Light dependant resistor (High light is low
resistance)
Thermistor – Heat dependant resistor (High heat
is low resistance)
D – variable resistor.
D- Variable resistor.
Meters and their places
Voltmeters measure potential difference and are
placed in parallel.
Ammeters measure current and are placed in
series.
State what is measured by the meters.
(2)
Meter 1 measures
..........................................................................................................................
Meter 2 measures
(ii) The meter that measures potential difference
is (1)
A in parallel with the power supply
B in parallel with the lamp
C in series with the lamp
D in series with the component X
Complete the circuit below with an ammeter
and a voltmeter correctly connected.
The power supply, variable resistor and lamp
symbols are already drawn for you. (3)
B in parallel with the lamp
correct symbol for ammeter or
voltmeter (seen anywhere) (1) one
meter connected in parallel with
lamp/variable
resistor/supply and one meter in
series with lamp(1) both meters
correctly connected (ammeter in
series and voltmeter in parallel with
lamp)
(1)
Ignore gaps, lines through symbols
and wire connected to side of
variable resistor Symbols do not
have to be correct for this mark
voltmeter connected across both
components is same as voltmeter
connected across supply Symbols
do not have to be correct for this
mark any shape, labelled ammeter,
in series with lamp AND any shape,
labelled voltmeter, in parallel with
lamp gains marking points 2 and 3
Graphs and formula – model an
answer.
Complete these points then do a line of best fit.
0.20
0.31
2.0
4.0
curve of best fit judged by eye Must pass through zero and
(1)
two other points.
5th point can be either
(8.0,0.42)
or
(8.0, 0.44)
straight line of
best fit through origin
tolerance between lines A
and B shown on the diagram
5th point can be either
(8.0,0.42)
or
(8.0, 0.44)
(c)(i point correctly plotted at 2.0, 0.14 to within
) half a small square (1) smooth curve of
best fit connecting all given points within
half a small square (1)
(c)(i a description including two of the following:
i) 
current increases as voltage
increases (1)

current is not proportional to the
pd (1)

gradient gets less (1)
Judge curve by eye.
If more than one line present then ignore
any that appear to be erased or deleted.
Ignore any part of line which goes beyond
given points.
If plotted point is incorrect then allow ecf for
line
(2)
Allow reverse argument positive correlation
(between them ) graph is not a straight line
not in equal steps current does not increase
as much (as it gets higher) accept resistance
has increased with increase in current for
two marks
(2)
(c)(i a suggestion to include: there is still a
ii) current (when control is at min position) (1)
make the battery last longer (1)
to break the circuit
to switch the current off accept flow of
electricity/charge/electrons for current
battery / energy would be drained /used up/
wasted otherwise accept reverse arguments
ignore reference to power / volts
(2)
A description including

resistance changed (1)

reduced/decreased/lowered (1)
OR

voltage/p.d /EMF (of
supply) changed (1)

increased /turned
up/higher(1)
remove (variable) resistor
/component X (2)
number of batteries/number of
cells
add another cell/battery/battery
pack/power pack/power supply (2)
substitution (1)
10/0.44 or 250/11 evaluation (1)
23 (ohms)
give full marks for correct
answer, no working
22.7(ohms),22.73 (ohms),
22.72(ohms)
Ignore excessive decimal places.